Soriano had singled with two outs in the Cubs third, the first hit off New York Mets pitcher Tom Glavine. Ryan Theriot then singled to center, and Soriano started running. About four steps after rounding second base, Soriano pulled up and tried to hop to third on his left leg. He was subsequently tagged out by Mets third baseman David Wright.
The 41,599 at Wrigley Field were silent as Soriano was helped off the field.
"A lot of things run through your mind," Chicago's Mark DeRosa said about seeing Soriano limp off the field. "When one of your best players pulls up like that -- you've seen guys pull up before but it seemed like he was in agony. You don't like to see that.
"Somebody is going to have to step up," DeRosa said, "and we're going to have to come together as a team and pick up the slack and hope he gets back as soon as possible but I know it's going to be awhile."
Soriano underwent an MRI on Sunday night.
"He's not going to be out there any time soon," Cubs manager Lou Piniella said. "It's probably going to be a minimum of two weeks and probably as long as a month."
The outfielder, sidelined earlier this season with a strained left hamstring, was batting .297 with 18 homers and 42 RBIs, and his single ended an 0-for-9 streak. He was 21-for-88 in his last 20 games.
The Cubs are one game behind the Milwaukee Brewers in the Central Division, and were hoping Soriano, whom they signed for $136 million this offseason, could get hot in the stretch to help.
"We've got two months left," Chicago's Jason Kendall said. "We have a good enough group of guys in here to keep going. It's part of baseball. You hope he's all right -- but you've got to keep going."
The team struggled last year when Derrek Lee was lost to a wrist injury in mid-April. This Cubs team is different, Lee said.
"We're a lot more talented, a lot deeper," he said. "We can't use [losing Soriano] as an excuse."
The Cubs could call up outfielder Felix Pie from Triple-A Iowa, move Theriot into the leadoff spot, and see if someone can pick up the offensive slack. All of that will likely be decided on the plane ride to Houston, where the Cubs will open a three-game series Monday night. They lost, 8-3, to the Mets and Glavine, who picked up his 300th career win, and finished the homestand against Philadelphia and the first-place Mets, 3-4.
"We would've liked to have done a little better," Piniella said. "We didn't lose any ground but we have to continue to play. Losing Soriano is the toughest thing about this homestand."
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.