SAN FRANCISCO -- Buster Posey hasn't yet played an inning at first base, but he'll spend some time there by the end of the season, manager Bruce Bochy said Wednesday.

Posey has started 32 regular-season games at first base, mostly in the middle of the 2010 season before Bengie Molina was traded to Texas.

Playing Posey at first would conceivably give the Giants another right-handed bat in the lineup when they face tough left-handers. Under this circumstance, Brett Pill likely would play left field, adding to San Francisco's right-handed-batting complement.

Philadelphia's Cliff Lee, Wednesday's starter, is as tough a left-hander as they come. But Bochy sought a balance between offense and defense, so he started Pill at first base, kept Posey behind the plate and left the outfield of Melky Cabrera, Angel Pagan and Nate Schierholtz intact.

"Putting Buster on first base adds an option," Bochy said. "But I did not want to do that tonight."

Wilson set for Tommy John surgery Thursday

SAN FRANCISCO -- As anticipated, Giants closer Brian Wilson will undergo reconstructive surgery, commonly known as Tommy John surgery, to repair his right (throwing) elbow Thursday.

Famed orthopedist James Andrews will perform the procedure on Wilson, 30, at his Pensacola, Fla., clinic. Giants team orthopedist Ken Akizuki will be on hand to assist. Andrews also handled Wilson's first Tommy John surgery in 2003. Wilson resumed pitching in 2004, made his Major League debut two years later and proceeded to make three National League All-Star teams.

Asked whether Wilson could resume pitching after about a year, which would be an accelerated recovery, Giants head athletic trainer Dave Groeschner remained noncommittal.

"I guess anything's possible, but we'll see after the surgery," Groeschner said.

Wilson pitched erratically but recorded a save last Thursday at Colorado. One day later, he informed the Giants' medical staff of his physical discomfort. The Giants then made Wilson's injury public Saturday while declaring him out for the season.

Right-hander Santiago Casilla has inherited the closer's role in Wilson's absence. Casilla pitched a shutout ninth to save San Francisco's 4-2 triumph Tuesday over Philadelphia.

Manager Bruce Bochy said that he expected Wilson to rejoin the team during its 10-day, nine-game homestand that starts April 27.

Hensley quickly a key part of Giants' bullpen

SAN FRANCISCO -- Clay Hensley already has established himself as a reliable member of the Giants' trusty bullpen. And with Brian Wilson sidelined, the Giants welcome the depth Hensley provides.

"It helps when you have another experienced guy who isn't afraid and wants to be in there with the game on the line," Bochy said.

Hensley went unscored upon in his first four appearances, which spanned 3 1/3 innings. He struck out six and allowed just one hit.

Hensley demonstrated his value in Tuesday's 4-2 victory over Philadelphia, relieing Madison Bumgarner with a runner on first base and nobody out. Hensley retired all three batters he faced, striking out Shane Victorino and Jimmy Rollins in the process.

Hensley performed like this in 2010, recording a 2.16 ERA with 77 strikeouts in 75 innings over 68 appearances with Florida. But a freak rib injury derailed him last year, when his ERA ballooned to 5.19. The Giants gladly signed him as a free agent on Jan. 26.

"He had a lot of success setting up," said Bochy, who managed Hensley in 2005-06 with San Diego. "He wants to be in that hold situation."