"Washington Nationals third baseman Ryan Zimmerman will undergo surgery Tuesday to repair a torn abdominal muscle and "if all goes well," he will return in six weeks, General Manager Mike Rizzo said. Zimmerman has already missed 17 games since he hurt himself sliding into second base April 9, an injury the team originally believed to be a severe strain.

Zimmerman has tried to rehab the injury, most recently playing catch with athletic trainer Lee Kuntz. Experiencing a dearth of progress, Zimmerman and the Nationals decided mutually for him to see specialist Bill Meyers in Philadelphia on Friday. Meyers diagnosed a tear of the rectus muscle — commonly known as the "six pack" — and it requires surgery, which will be performed Tuesday in Philadelphia.

"We did everything we could to try and avoid it, which is the first step, always," Zimmerman said. "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 and let this guy do it and get back to the road to coming back and helping the team win."

Already missing their best pitcher, Stephen Strasburg, for the entire season as he rehabs from Tommy John surgery, the Nationals also will miss Zimmerman for, at best, about 60 games this season. The Nationals have gone 9-8 without Zimmerman, their undisputed best player, as veterans Jerry Hairston and Alex Cora have filled in.

"We see one of the best hitters in baseball that's not going to be able to play for us for six weeks," Rizzo said. "We're scratching for runs and trying to win games. The guys that we've put out at third base have been terrific defensively and we've struggled to score runs. When you take your best hitter out of the lineup, you're going to have to find different ways to score runs. Nobody's going to feel sorry for us."

"It's frustrating," right fielder Jayson Werth said. "It's one of those things he's been dealing with since spring training. Hindsight is 20/20. You could look at it like, he could have got it done then and we would have him now. But you can't second-guess these things. It's a tough injury to really gauge. Hopefully, he'll get the surgery and be back soon."

Zimmerman first missed three games early in spring training with a minor tweak he called "a non-factor" at the time. Later, he missed more than a week with a groin strain that was related to the abdominal strain, Nationals team physician Wiemi Douoguih said."