FORT MYERS, Fla. — Jonathan Papelbon was the game’s best closer last season, but he’s intent on improving. If he doesn’t, he fears, the hitters will gain on him.

Papelbon went into the offseason with the idea of adding a third pitch to his fastball and split-finger fastball and chose the slider.

Yesterday, in his second appearance of the spring, he used it to get two of the three outs he recorded in the fourth.

“That was a big step for me,” said Papelbon after the Sox beat the Pittsburgh Pirates, 5-3. “I’m getting depth on it. I feel like I can start the season as a three-pitch closer. I want to be able to throw it anytime, in any count, against any hitter. There were times last year I could have really used (a third pitch).”

Papelbon converted 37 of 40 save opportunities last season and was unscored upon in the postseason, but feels he can’t stay stagnant. If he doesn’t give the hitters a different look at times, eventually they’ll catch up to his stuff.

“You’ve got to keep (opposing hitters) on their toes,” he said. “If I can add that, I have another bullet in my arsenal. These hitters are so good, if you don’t keep one step ahead of them, they’ll bury you.”

“You’re not going to see him change his style,” said manager Terry Francona, “but sometimes there are guys sitting on a fastball and he can throw (the slider) for a first-pitch strike.”

Around the bases

The Sox are dealing with a couple of nagging injuries. Outfielder Coco Crisp has a slight groin strain while Julio Lugo has some tightness in his back. Both sat yesterday, with Jacoby Ellsbury in center and Argenis Diaz at short. Both Crisp and Lugo could return to the lineup today when the Sox host Cincinnati. … Diaz had a strong game, collecting three hits, knocking in two runs and scoring one. … The club hosted 35 young cancer patients from the Dana Farber Institute in Boston as part of the team’s Jimmy Fund affiliation. The patients met with some players yesterday morning, then watched the game from a suite. … Craig Hansen, who had a horrendous outing against Minnesota over the weekend — one inning, three walks, one hit batsman, four runs allowed — rebounded yesterday to pitch a scoreless inning in relief. … In order to provide themselves with another opportunity to evaluate the pitchers in camp, the Sox are putting together a four-inning camp game for Saturday morning. The Sox will use a major-league battery — pitchers and catchers — and the rest of the players will be borrowed from the minor-league camp. That came after both the Twins and Reds — the two teams closest to the Sox geographically — were unable to accommodate a “B” game. … David Ortiz spent a portion of the morning consoling his wife, Tiffany, a die-hard Green Bay Packers fan, after news spread that Brett Favre had elected to retire. … The team will probably make the first round of cuts sometime later this week. The Sox have 56 players in camp. … Homer Bailey, one of the game’s top-ranked pitching prospects, will start for the Reds this afternoon. Scheduled for the Sox: Jon Lester, Javier Lopez and Manny Delcarmen.

smcadam@projo.com