BOSTON -- Clarke MacArthur was on his way to retirement, having moved to Florida thinking his playing days were gone because of concussions.

Suddenly, he started feeling better.

Sunday, the 32-year-old winger scored a power-play goal 6:30 into overtime to give Ottawa a 3-2 Game 6 victory over the Boston Bruins that sent the Senators into the second round.

"There's nothing like living in the NHL and living in these playoffs," MacArthur said after his second goal of the series sent his team into the Eastern Conference semifinals against the New York Rangers. "It's something (retirement) everyone's going to have to deal with one day, but I want to stretch it out as long as I can, obviously."

MacArthur, who returned for four regular-season games and earlier in the series celebrated his comeback with his first goal in two years, sent a Bobby Ryan rebound past Tuukka Rask for the winner.

"You get opportunities like that to put them away, you've got to put them away," MacArthur said. "It's just awesome that we were able to."

All six games of the series were decided by one goal, four in overtime, and Sunday marked the Senators' sixth straight win at TD Garden. Ottawa won eight of 10 games against Boston this season and all were close.

Craig Anderson made 28 saves for Sunday's deciding win.

Ryan and Kyle Turris also scored for the Senators. Ryan scored his fourth goal in the six games, his fifth in the last seven dating back to the regular season finale, when he broke a 13-game goal drought.

Erik Karlsson, who had been held in check by the Bruins in Games 5 and 6, turned it on and was everywhere in the overtime -- his rush down the right side ending when David Pastrnak pulled MacArthur down leading to the Ottawa win.

"My first experience (in the playoffs), I ended up in the box on the last game of the season," Pastrnak said.

After the game, Karlsson revealed he played the entire series with two hairline fractures in his left heel.

Karlsson, the Ottawa captain, sang MacArthur's praises, saying, "Very well-deserved I think. Being gone for as long as he had, stepping in late in the season, and playing the way that he is. It just shows what a good character guy he is, how much he wants to be a player and be a good player for this club."

MacArthur said Sunday's win helped erase "some nightmares" he experienced when he was with the Toronto Maple Leafs blew a 4-1 lead and lost a Game 7 to the Bruins in 2013.

"It's nice to be on the other side," he said.

Drew Stafford and Patrice Bergeron scored for the Bruins, with Brad Marchand assisting on both goals. Marchand, who has scored 76 goals in the last two seasons, scored just one in the series and has one in his last 26 playoff games.

"We battled hard," said Rask, who made 26 saves. "Ever since after the coaching change, we really came together as a group. We got in the playoffs and then played a heck of a series. I think every game was a one-goal game, so it was a hard-fought series and just didn't go out way. I think everybody here should be proud the way we battled."

Bruce Cassidy took over for the fired Claude Julien on Feb. 7 and coached the Bruins into the playoffs with an 18-8-1 record while carrying the interim label, was asked after the game if he wants to return.

"Absolutely -- one hundred percent," he said.

The Bruins scored their first first-period goal -- also scoring first for the first time in the series -- when Stafford converted on a power-play slapper with 1:47 left in the period.

The Senators struck twice in the second period.

Even though they had fewer regular season points than New York, The Senators will have home ice advantage by virtue of finishing second in the Atlanta Division while the Rangers are a wild card.

The Sens went 2-1 against the Rangers this season.

NOTES: According to STATS, Inc., the three delay-of-game penalties on the Bruins marked the first time since 1989-90 a team did it three times in a first period, the fourth time it was done in any period. The Pittsburgh Penguins had three in a span of 2:02 in the third period of a playoff game last season. ... Bruins C David Krejci was out with a lower-body injury sustained in Game 5. He was limited to only two full games in the series. LW Matt Beleskey was back in for his third game in the series. ... D Chris Wideman, who injured Krejci in a collision, was also injured but was listed as a healthy scratch. D Fredrik Claesson dressed for the second time in the series. ... Ottawa LW Viktor Stalberg, a game-time decision after the skate, dressed, as did Tommy Wingels, in for his second game. LW Tom Pyatt and D Mark Borowiecki remained out with injuries.