An abdominal injury to Washington Nationals third baseman Ryan Zimmerman that first surfaced as a minor nuisance in spring training is now a tear that requires surgery and will sideline him for about six weeks.

"It's to the point right now where it hasn't been getting better, to the point where you might as well go in there and fix it," Zimmerman said Saturday.

"It's just one of those things where it was continuing to linger," he added, "and it's so early in the season that to get this done and to get back in six weeks — or whatever they say it was — it just makes sense, instead of trying to deal with it all year."

General manager Mike Rizzo said Zimmerman will have surgery in Philadelphia on Tuesday.

The injury first occurred during spring training, although Zimmerman said he couldn't pinpoint the exact timing. He then aggravated it early in the regular season. The 2009 NL Gold Glove winner originally went on the 15-day disabled list on April 12, with what the Nationals said at the time was a strained abdominal muscle.

But the injury never improved, and Zimmerman got a second opinion from a doctor in Philadelphia on Friday.

"It started out very minor, back in the beginning of March," Nationals team doctor Wiemi Douoguih said. "We shut him down, stopped the baseball activity and then brought him back, and he wasn't having any problems. He was getting better every day and then slid into second base in the first or second week of April and it really got much worse after that, and that's when we shut him down."

Zimmerman has played in only eight games this season, hitting .357 with a triple, one homer and four RBIs.

"It started off as a strain. When I was playing through it, it was a strain," he said. "That's one of the reasons why we felt if we continue to rehab it, it will get better."

Zimmerman is generally considered Washington's best all-around player, usually hitting No. 3 in the lineup and providing top-notch defense. And as the Nationals' first draft pick when the club moved from Montreal to Washington, he quickly became the face of the franchise.

The Nationals have been forced to turn to veteran reserves Jerry Hairston Jr. — who started Saturday against the World Series champion San Francisco Giants — and Alex Cora to play third base. Jayson Werth has been batting third in Zimmerman's place.

"We see one of the best hitters in baseball that's not going to be able to play for us for six weeks. We're 9-8 without him. We're scratching for runs and trying to win games," Rizzo said before Saturday's game. "The guys that we've put out at third base have been terrific defensively, and we've struggled to score runs. Obviously when you take your best hitter out of the lineup, you're going to have to find different ways to score runs."