BOSTON (AP) -With a few more performances like this, the Bruins will be in the same mode as the Flyers - winding down the season.
"Totally ridiculous. Unacceptable," Boston coach Dave Lewis said. "It's something that drives you nuts as a coach, knowing the situation, the standings and who we're playing."
The Bruins, 13th in the Eastern Conference - seven points behind eighth-place Montreal for the final playoff spot - looked like a team that's about to complete its second straight season without a postseason appearance.
"We're still in the hunt and we've got to play a lot harder to get ourselves in that position," Lewis said.
Joni Pitkanen, R.J. Umberger and Mike Richards had the Flyers' goals. Philadelphia snapped a five-game losing streak.
Mark Mowers ended his stretch of 27 games without a goal by scoring a pair for Boston, and defenseman Zdeno Chara had his 10th of the season.
Martin Biron, acquired from Buffalo on Tuesday for a second-round pick in the 2007 draft, made 34 saves in his Flyers' debut. He made a right pad save on Petr Tenkrat's clean breakaway bid with just under 15 minutes to play.
"We have a young team that makes a lot of mistakes, but we're learning," Biron said. "It was a big step for this team."
Upshall, sent in on a partial breakaway on a pass from Sami Kapanen, slipped around defenseman Andrew Ference before shifting to his backhand and putting the puck behind Thomas for the game-winner.
"It was a hightlight-reel play," Flyers coach John Stevens said of the goal for a team that's had few great moments.
The Flyers have a league-worst 44 points.
Philadelphia, which trailed 2-0 after the game's opening 8:09, won for just the second time in an overtime game this season.
The Bruins were outshot 55-37 and have allowed over 50 shots on goal in two of their last three games. Boston dropped its third straight after a four-game winning streak seemingly got it back in the playoff race.
"As the game went along I was - along with my teammates - trying to do anything we could to get the two points," Thomas said.
Boston jumped ahead 1-0 on Mowers' first goal of the game - and his first since Dec. 29 - 4:10 into the opening period. They made it 2-0 when Mowers beat Biron with a wrister from the right circle 3:59 later.
Mowers, who entered the night with just two goals all season, also went 24 games without a goal after scoring in Boston's second game of the season.
The Flyers cut it to 2-1 on Pitkanen's score midway into the opening period.
Philadelphia, which owned a 21-10 shot advantage in the second period, tied it 2-2 when Umberger scored off a rebound in front for a power-play goal at 4:53.
Richards completed a 2-on-1 break for a short-handed score by beating Thomas inside the right post before he could get across, making it 3-2 at 11:33.
Boston tied it at 3-3 on a two-man advantage at 12:36 when the 6-foot-9 Chara scored out of a scramble in front by outmuscling a defender.
Boston's newcomers Aaron Ward, acquired from the Rangers for defense Paul Mara on Tuesday, and Dennis Wideman, picked up from St. Louis for winger Brad Boyes, also before the trading deadline, saw their first action with the Bruins.
Notes: Mowers also had just two assists in his last 22 games. ... Boston RW Glen Murray played after missing the last four with a groin injury. ...The fans gave a loud ovation to the crew members of the USS John F. Kennedy, which is currently in Boston, when they were recognized on the video board. ... It was a matchup of two of the league's three teams that have allowed the most goals, with Philadelphia having given up the most overall.
|Mark Mowers (3) Slapshot - ASST: Dennis Wideman (18)|
1 - 0 BOS
|Mark Mowers (4) Wrist shot - ASST: Jeremy Reich (1)|
2 - 0 BOS
|Joni Pitkanen (3) Wrist shot - ASST: Mike York (10), Mike Richards (16)|
2 - 1 BOS
|PPG - R.J. Umberger (15) Slapshot - ASST: Derian Hatcher (4), Geoff Sanderson (14)|
2 - 2 Tie
|SHG - Mike Richards (5) Wrist shot - ASST: Sami Kapanen (9), Denis Gauthier (3)|
3 - 2 PHI
|PPG - Zdeno Chara (10) Slapshot - ASST: Marco Sturm (14), Marc Savard (62)|
3 - 3 Tie
|Scottie Upshall (5) Wrist shot - ASST: Sami Kapanen (10)|
4 - 3 PHI
|Jeremy Reich Hooking|
|Stefan Ruzicka Hooking|
|Zdeno Chara Tripping|
|Petr Tenkrat Hooking|
|Stefan Ruzicka Hooking|
|Jeff Carter Slashing|
|Denis Gauthier Boarding|
|Patrice Bergeron Roughing|
|Marco Sturm Hooking|
|Scottie Upshall Hooking|
|Dennis Wideman Hooking|