NEW YORK -- After another disappointing outing by a taxed bullpen, the Mets will add two relievers to their roster before Monday's game against the Rockies.

Jason Isringhausen, who was drafted by the Mets in 1991 and made his Major League debut with the club in 1995, will join Ryota Igarashi in making the trip to Queens. To clear room on their roster, the Mets designated Blaine Boyer for assignment and optioned Lucas Duda to Triple-A Buffalo. Boyer took the loss in relief to the Nationals on Sunday after allowing four runs in two innings.

"Right now, we need some innings," Mets general manager Sandy Alderson said following Sunday's 7-3 loss. "Based on today, we were short coming in, we're shorter now and we're not getting the kind of results that we need."

Alderson said the move to 13 pitchers will likely be temporary until the return of left fielder Jason Bay, who is rehabilitating an oblique injury. Bay took batting practice Sunday.

"Could be this weekend," Alderson said of Bay's return. "But right now we need the arms. In Izzy's case, it's kind of a one-way trip. It would be difficult to move him off the roster if things didn't work out. In Igarashi's case, he has options, so theoretically if we put him on the roster, we could option him out, but that is all premature at this point."

The Mets could not recall Manny Acosta since he was designated for assignment within the last 10 days. No player removed from a 25- or 40-man roster is eligible to be recalled to his Major League club unless another player is assigned to the disabled list.

"Problem No. 2 is he hasn't pitched in the time since he was designated for assignment, so he's not really ready; he's not even available," Alderson said of Acosta. "Obviously, he's there for us, continues to be there in reserve, but given the circumstances, we can't really get him back."

Isringhausen hasn't pitched in a Major League game since 2009 with the Tampa Bay Rays, but the Mets' bullpen has not impressed so far this season. Igarashi appeared in 34 games for New York last season, posting a 7.12 ERA. He has made two appearances for Triple-A Buffalo this season.

"It's been inconsistent," Alderson said of the bullpen. "Probably as positive an adjective as I can use. But it's unfortunate. It's one of those things. It's going to happen over the course of the season. Hopefully we'll get a couple of other arms in here and settle things down a little bit, and it won't be as stretched as it has been the past couple of days.

Isringhausen has battled through injuries throughout Spring Training and agreed to stay in Port St. Lucie, Fla., after the team broke camp.

"He's put in a lot of work and deserves the opportunity, and it's time for us to give him a shot."

Suspension over, Paulino lands on DL

NEW YORK -- After finishing out a 50-game suspension from last season, Mets catcher Ronny Paulino will now spend at least 15 days on the disabled list after anemia prevented him from being ready for Sunday's home game against the Nationals.

Mets general manager Sandy Alderson, who is hoping to prepare Paulino as a platoon partner with catcher Josh Thole, said Paulino would begin his rehabilitation in Port St. Lucie, Fla. He will likely begin playing in games there on Thursday before moving on to Triple-A Buffalo. He will be eligible to return from the DL on April 26, when the Mets visit Washington. The Mets were not allowed to backdate Paulino's time on the DL because of his suspension.

"It's tough in the sense that we didn't really have any other choices," Alderson said before Sunday's game. "He's just not really ready to go. If we were to activate him now, and he sits for two or three days at a time, we may never get him game ready."

Paulino is recovering from anemia, or a shortage of hemoglobin in his blood. Mike Nickeas has been serving as the Mets' backup catcher in his absence.

"His blood count is up to an acceptable level -- far higher than it was at the time of his physical," Alderson said. "And it's high enough for the doctors to clear him for activity. We expect those blood counts will continue to go up, but at the moment, he's cleared for activity."

Paulino signed with the Mets in the offseason after two seasons with the Marlins. When he returns, he will likely see much of the playing time against left-handed starters. In 531 career plate appearances against lefties, Paulino has a .338 batting average and a .391 on-base percentage. Against right-handers, those numbers fall to .245 and .301.

Last season, Paulino hit .259 with a .311 on-base percentage in 344 plate appearances with the Marlins.

Collins sticking with rest plan for Beltran

NEW YORK -- Mets manager Terry Collins is sticking with his plan of rest for Carlos Beltran, but he's hoping warmer weather helps minimize the numbers of days off required by the right fielder.

As Collins promised, Beltran did not start Sunday's series finale against the Nationals, even after his two homers Saturday night helped lift the Mets to their first home victory of 2011.

"He's the only one who knows how he feels," Collins said. "After the game I went in there and visited, and he just said he'd like to stay with what we discussed. That's what he thinks is best, and we'll continue on with that."

Sunday's game began with a temperature of 54 degrees. Collins feels the cooler weather is more taxing on Beltran, who had microfracture knee surgery in the 2009-10 offseason and dealt with tendinitis during Spring Training this year.

"I think once things start to get warmer, we'll see it a little bit different," Collins said. "The next day, I think he'll feel a little bit different. I'm hoping maybe in Atlanta, they'll see how it goes, maybe a little warmer down there."

Third baseman David Wright and shortstop Jose Reyes, on the other hand, haven't had a day of rest yet this season. Although Collins feels the weather will help Beltran, that change in temperature may trigger more rest for the left side of his infield.

"Right now, with the cool weather, I just don't think they're going to get that worn down just yet," Collins said. "All Spring Training long, we did a pretty good job making sure those guys got plenty of rest. When it starts to warm up, I think you'll start to look for those guys to get a day off now and then."