The Boston Bruins had a, 2-0, lead after the first period, but allowed the Ottawa Senators to score three unanswered goals after B’s goaltender, Linus Ullmark, left the game due to injury Thursday night at TD Garden.

Tim Stützle scored the game-winning power-play goal midway through the second period, while Anton Forsberg (19-16-3, 2.73 goals-against average, .919 save percentage in 41 games played) made 40 saves on 42 shots against in the victory for Ottawa.

Ullmark (23-10-2, 2.57 goals-against average, .913 save percentage in 38 games played) made eight saves on eight shots faced for Boston before being replaced by Jeremy Swayman (20-12-3, 2.38 goals-against average, .915 save percentage in 36 games played) after the first intermission.

Swayman stopped 21 out of 24 shots against in the loss for the Bruins.

After the game, B’s head coach, Bruce Cassidy, told reporters that Ullmark “didn’t feel well” after taking a shot off the face mask in the first period.

Prior to Thursday night, the Bruins were the only team across the National Hockey League that had yet to lose three consecutive games this season.

As a result of the loss, Boston dropped to 45-24-5 (95 points) overall, but remain in command of 4th place in the Atlantic Division, as well as the first wild card spot in the Eastern Conference– though for the second game in-a-row, the B’s failed to clinch a playoff berth.

There’s not too much to worry about, however, given the long shot odds of the New York Islanders dethroning either the Bruins or the Washington Capitals for a wild card playoff berth.

With nine games remaining in New York’s schedule, the Islanders would need to win all nine games and hope for a colossal collapse of either the Capitals or Bruins in their remaining eight games.

Washington would have to amass no more than three points over the remainder of their schedule, while Boston would have to lose every game for the Isles to make the 2022 Stanley Cup Playoffs.

New York might have better odds playing the lottery or tuning into New York Rangers playoff games if they’re hoping to see some postseason action this spring.

Meanwhile, the Senators improved to 28-40-6 (62 points) on the season and remain in command of 7th place in the Atlantic Division.

Boston finished their regular season series against Ottawa with a 3-1-0 record in their four meetings.

The Bruins did not play the Senators in 2020-21 due to the temporarily realigned divisions and condensed 56-game schedule in accordance with COVID-19 restrictions.

The B’s went 2-1-0 against the Sens in 2019-20.

Jakub Zboril (right ACL), David Pastrnak (undisclosed) and Hampus Lindholm (lower body) were joined by Brandon Carlo (undisclosed) on Boston’s list of injured players out of the lineup against Ottawa on Thursday.

Jack Ahcan and Jesper Frödén were recalled from the Providence Bruins (AHL) on Tuesday and Wednesday, respectively, prior to Thursday night’s action.

Meanwhile, Matt Grzelcyk returned to the lineup on defense and took part in his 300th career NHL game– suiting up in his regular role on the second pairing.

Cassidy made a few changes to his lines– inserting Frödén on the second line with Taylor Hall at left wing and Erik Haula at center, while promoting Tomáš Nosek to the third line in Trent Frederic’s usual spot.

Frederic served as a healthy scratch on Thursday, while Marc McLaughlin was demoted from the second line right wing to centering the fourth line with Nick Foligno and Curtis Lazar as his wings.

On defense, Mike Reilly was paired with Charlie McAvoy, while Grzelcyk and Josh Brown started the night out as Boston’s top-four defenders.

Derek Forbort and Connor Clifton served as the third pairing.

Frederic was joined by Jack Studnicka, Ahcan and Anton Blidh in the Bruins press box as healthy scratches against the Senators.

Early in the opening frame, Boston worked the puck deep into the zone whereby Foligno wrapped around the net and spun a backhand shot pass to the slot for McLaughlin (3) to redirect on the doorstep past Forsberg’s right pad.

Just like that, the Bruins had a, 1-0, lead at 6:36 of the first period, while Foligno (11) and Lazar (8) tallied the assists– marking Foligno’s 499th career NHL point in the process.

Less than a minute later, the Senators had too many skaters on the ice and presented the B’s with the first legal skater advantage of the night at 7:15, but Boston couldn’t convert on the ensuing power play.

Late in the period, Travis Hamonic elbowed Haula and was assessed a minor infraction at 15:20, but once again the Bruins failed to capitalize on the resulting power play.

Just as the final minute of the period was being announced, Grzelcyk corralled a loose puck at the point and kept the play in the attacking zone before sending a shot towards the net with traffic.

Frödén (1) deflected Grzelcyk’s bullet from the blue line and gave Boston a two-goal lead at 19:01 of the first period.

Grzelcyk (19) and Hall (39) had the assists as the Bruins took a, 2-0, lead into the first intermission.

Boston had a 2:1 advantage in shots on goal, outshooting the Sens, 16-8, in the first period, while leading in giveaways (6-2) and faceoff win percentage (71-29) as well.

Ottawa held the lead in takeaways (3-1) and hits (12-7) after one period, while both teams amassed two blocked shots each heading into the middle frame.

The Bruins were 0-for-2 on the power play and the Senators had yet to see time on the skater advantage.

Swayman replaced Ullmark for the start of the second period after Ullmark briefly skated over to the bench upon taking a shot off the mask in the first period and checked in with a trainer before returning to the crease.

Ullmark did not return to the game and was not seated on Boston’s bench for the rest of the night either– marking the fifth time in the last six games that someone left the action with an injury for the Bruins.

Less than a minute into the second period, Swayman was tested and gave up a goal when he apparently hadn’t covered enough of the short side as Brady Tkachuk (27) won a battle to the puck by knocking down McAvoy as the two skaters raced to the loose puck at the endboards prior to banking the rubber biscuit off of the Bruins netminder and into the twine.

Stützle (31) had the only assist on Tkachuk’s goal as the Sens trailed, 2-1, 47 seconds into the middle frame.

Less than a minute later, Boston had too many skaters on the ice and had been assessed a bench minor as a result.

McLaughlin skated over to the sin bin to serve the infraction at 1:22 and the Bruins managed to kill off Ottawa’s power play without issue.

The same could not be said for their next two penalties as Reilly caught Tkachuk with a high stick at 8:39 and Patrice Bergeron went to the box for hooking at 8:46 of the second period.

The Senators had a 5-on-3 advantage for a little less than two full minutes and they put Boston through the ringer as a result.

First, Drake Batherson fed Josh Norris (33) through the slot for a one-timer from inside the circle to Swayman’s left side– tying the game, 2-2, in the process on Norris’ power-play goal.

Batherson (25) and Stützle (32) tallied the assists at 9:30 of the middle frame.

Less than a minute later, the Bruins struggled to get the puck out of their own zone before Stützle again factored on the play– dishing the puck back to the point prior to the Senators sending it in towards the goal line to establish a traingle setup in the offensive zone.

Tkachuk fired a shot that rebounded as Stützle (18) collected the garbage while crashing the slot– giving Ottawa their second power-play goal as a result.

Stützle factored into all three Senators goals with a goal and two assists in Thursday night’s effort, while Tkachuk (31) picked up the assist on Stützle’s game-winning goal as the Sens grabbed a, 3-2, lead at 10:27 of the second period and held onto it for the rest of the night.

Batherson served a hooking penalty at 13:45 of the middle frame, but the Boston failed to get another shot past Forsberg as the power play came and went without issue for Ottawa’s penalty kill.

Late in the period, Brad Marchand tripped Connor Brown and cut a rut to the box, though the Senators failed to convert on the power play at 17:56.

Through 40 minutes of play, Ottawa had a, 3-2, lead on the scoreboard, despite trailing Boston in total shots on goal, 24-23.

The Sens, however, had a, 15-8, advantage in shots on net in the second period alone.

Ottawa also led in blocked shots (7-6), takeaways (6-3) and hits (20-17) after two periods, while the Bruins led in giveaways (9-5) and faceoff win% (61-40).

Heading into the final frame, the Senators were 2-for-4 on the power play, while the B’s were 0-for-3 on the skater advantage.

Colin White tripped Craig Smith to give Boston a power play at 5:24 of the third period, but the Bruins couldn’t convert on the advantage in keeping with the theme of the night.

Lazar was assessed a roughing minor for trying to engage Parker Kelly in an exchange of fisticuffs after Kelly made a big hit in the neutral zone, but the Senators ended up on the power play instead at 9:15 of the third period.

Ottawa failed to capitalize on their second-to-last advantage of the evening.

Artem Zub was assessed an interference infraction at 13:52, but the B’s continued to be shutdown on the power play.

Late in the period, the Bruins once again had too many skaters on the ice at 15:27 and Nosek skated over to serve the bench minor in the box.

The Sens did not capitalize on the resulting abbreviated power play, however, after 26 seconds of 4-on-4 play.

With 1:29 remaining in the action, Swayman vacated the crease for an extra attacker after putting an end to several breakaways for the Senators.

After a stoppage with 39.9 seconds remaining, Cassidy used his timeout to allow assistant coach, Chris Kelly, to talk to his skaters and draw up a plan for winning a last-ditch offensive zone faceoff.

Things did not go according to plan and the puck rolled out of the attacking zone with about 10 seconds left on the clock.

At the final horn, Ottawa had won, 3-2, despite finishing the night trailing in shots on goal, 42-32. Boston had an, 18-9, advantage in shots on net in the third period alone.

The B’s left their own ice leading in blocked shots (10-6), giveaways (10-7) and faceoff win% (68-32), while both teams managed to amass 30 hits each.

Ottawa finished the night 2-for-6 on the power play, while Boston went 0-for-5.

The Bruins fell to 33-9-2 (15-5-1 at home) when scoring first, 25-5-1 (12-3-0 at home) when leading after one and 4-18-2 (3-11-1 at home) when trailing after two periods this season.

The Senators, meanwhile, improved to 9-26-4 (5-13-2 on the road) when allowing the game’s first goal, 3-14-2 (3-7-2 on the road) when trailing after the first period and 21-1-2 (9-0-1 on the road) when leading after the second period in 2021-22.

The B’s wrap up their three-game homestand Saturday afternoon against the Pittsburgh Penguins before hitting the road for a pair of games in St. Louis and Pittsburgh next Tuesday and Thursday, respectively.

Boston returns home to host the New York Rangers next Saturday (April 23rd) in a game that will be broadcast across the United States on ABC.