The veteran had been sidelined since Feb. 25 with a strained left oblique. To make room for Timlin on the roster, lefty side-winder Javy Lopez was optioned to Triple-A Pawtucket.
"Whenever [manager Terry Francona] calls me is when I'll pitch," said Timlin. "There's no expectations. I feel fine."
Having Timlin back figures to further solidify the bullpen for the Red Sox.
"Well, the idea is, if we get the guy we can rely on, like we have so much, it's such a bridge to [Jonathan Papelbon]," said Francona. "Just like Pap made everybody better, Timlin makes everybody better. It's not so much eliminating guys from pitching, but it just makes their roles a little bit easier to be successful."
Would Francona go to Timlin on Tuesday with the game on the line?
"You know what, let's see where the game's at," Francona said. "We've got to look at maybe how we get there. We'll see. If there was a situation today where it was up or down, one way or the other, we could also use him. But if there's a chance to win the game, yeah, we probably would. But we wouldn't hesitate if it was lopsided either, just to get him an inning."
Timlin did appear in Tuesday's game, allowing two hits and two runs in the ninth.
Despite Lopez's move back to the Minor Leagues, Francona was impressed by the adjustments made by the lefty.
"We're thrilled," Francona said. "From the first day of Spring Training to the other day, we asked him to throw strikes and work ahead and be economical because of the deception in his delivery and he did that very well. This was, as we told Javy, a numbers thing. It wasn't the way he pitched."
Matsuzaka unveiled at Fenway: In what was hardly a shocker, Daisuke Matsuzaka got the loudest ovation during pregame introductions. Matsuzaka bowed and doffed his cap to the crowd.
During batting practice, Matsuzaka shook hands with Ichiro Suzuki, his teammate from the 2006 World Baseball Classic.
Papelbon, on the heels of Sunday's dramatic save in Texas, also got a thunderous ovation.
Red Sox legend Johnny Pesky got such a loud hand that he appeared to be on the verge of tears as he stood on the first-base line with the rest of the team.
Waiver pickup: In a move aimed at bolstering bullpen depth in the organization, the Red Sox claimed right-hander J.D. Durbin off waivers from the D-backs on Monday.
Durbin, who was designated for assignment on Tuesday, made one appearance for the Diamondbacks, giving up seven runs in two-thirds of an inning. The 25-year-old had spent seven years in the Minnesota Twins' system. If he clears waviers, he'll likely to start out at Triple-A Pawtucket.
"I think it's a way of trying to acquire an arm in the organization for depth," said Francona. "We had an open roster spot. I know [general manager] Theo [Epstein] has liked him for some time. Again, because we had the open roster spot, it just gives us a chance to add depth. That would be the whole idea. You sit here today and think, 'We don't need a pitcher.' We could sit here 10 days from now thinking we need three. That's kind of the idea."
Wily Mo on Thursday? Look for outfielder Wily Mo Pena to make his first start of the season on Thursday afternoon, when the Sox face Mariners lefty Jarrod Washburn.
Francona had hoped to get Eric Hinske a start in this series against Jeff Weaver, but those plans got changed with Seattle's rotation getting bumped back by all the snowouts in Cleveland. Weaver started Tuesday and Francona didn't want to rest one of his regulars for the home opener.
Hinske is 10-for-25 lifetime against Weaver.
Quotable: "When we're getting ready to lose." -- Francona, asked when it is appropriate to use Papelbon in the eighth inning
On deck: Matsuzaka will make his anticipated Fenway debut against Ichiro and the Mariners on Wednesday, with the first pitch scheduled for 7:05 p.m. ET. In what should be a riveting pitching matchup, the Mariners counter with right-handed ace Felix Hernandez.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.