Jonathan Papelbon's outstanding rookie season probably is over _ and his days as Boston's closer could be, too.

Sidelined by a sore shoulder since Sept. 1, Papelbon said Friday he doesn't expect to pitch again this season, and he's already planning a switch to the starting rotation next year.

``I'm probably going to be done for the year right now, unless something crazy happens,'' Papelbon said. ``I just think it's smart, especially with what happened to (Francisco) Liriano. He's a young pitcher. If we were in this thing still, I'd go out and pitch.''

Liriano, another contender for AL Rookie of the Year, recently missed a month of action due to an ailing elbow. The Minnesota Twins' left-hander tried to return from the injury, but left his comeback start Wednesday after only 28 pitches, saying he heard a pop in his elbow.

``The thing with Liriano has really opened up our training staff's eyes, and a lot of people's eyes in the major leagues,'' Papelbon added before Boston's scheduled game against the New York Yankees was postponed by rain Friday night.

It will be made up as part of a day-night doubleheader on Sunday, beginning at 1:05 p.m. The second game is slated for 8:05 p.m.

The teams are also set for a split doubleheader on Saturday, meaning they'll play four times in less than 36 hours.

Papelbon said the plan to become a starter next year is not definite _ but he was already thinking about joining the Red Sox rotation alongside Curt Schilling, Josh Beckett and Tim Wakefield.

``If you look at what's going on next year, Schilling, Beckett, me and Wake _ we could have something,'' Papelbon said. ``Nothing's set in stone, believe me. If we could go out and make a big acquisition, I'd be happy.

``We haven't really ironed out everything yet. This was kind of a quick conversation. They know I can start. I know I can start. I think they like, I like it, and I'll be able to run with it,'' he said.

The 25-year-old Papelbon has 35 saves in 41 chances. He is 4-2 with a 0.92 ERA in 59 appearances with 75 strikeouts and only 13 walks in 68 1-3 innings.

He came out of a game on Sept. 1 against Toronto after feeling pain in his pitching shoulder. Tests showed no major damage, and the right-hander has been resting his shoulder.

``I'm just trying to get my strength back,'' Papelbon said.

Looking ahead to next season, Papelbon said there are some things he won't miss about closing.

``I won't miss the stress. I'll miss the adrenaline. I'll miss getting the last out,'' he said. ``You've got to shift your thoughts. Starting's all about one day.

``I like pitching in general, whether it's starting or closing, it doesn't matter.''