Cordero will have an MRI in Miami on Friday to determine how serious the injury is.
"I know how hard the guy worked during the offseason to get the knee better," said teammate Jose Vidro, who is one of Cordero's close friends. "With him on the DL, hopefully, he will get better and we can get him back soon."
After the game, Cordero was spotted in street clothes on crutches. He declined to comment about the injury, but Dr. Bruce Thomas said that Cordero felt a pop in his left knee while running the bases. The only time he ran the bases was in the fourth inning when he flied out to center field.
"The area where he has the pain is in the medial meniscus. It's sort of the shock absorber of the inside part of his knee," Thomas said.
Thomas said if surgery was needed, Cordero would be out six weeks or more. If Cordero doesn't need to go under the knife, he will be out about a month.
Cordero, who the Nationals signed last offseason because of his leadership skills, had problems with his left knee when he was with the Marlins. Cordero had arthroscopic knee surgery on his left knee on May 25 last year to repair a torn medial and lateral meniscus. Thomas said Cordero was at high risk of having the same injury again.
"When you repair the meniscus, you do lose a little bit of that tissue. It makes it thinner. It makes it a higher risk of cracking again," Thomas said. "He has had it before. You can be fooled by the initial exam. He has some swelling there. We'll know a lot more by this time tomorrow."
With Cordero on the disabled list, the Nationals purchased the contract of infielder Carlos Baerga. Baerga was expected to start the season at Triple-A New Orleans.
The switch-hitting Baerga, who was invited to camp in February, played in 19 games for the Nationals during the exhibition season and went 8-for-35 (.229) with an RBI.
Baerga, who was the final cut in training camp last Friday, can play first and third for the Nationals.
"When we sent him down at the time, we told him that we wanted him," manager Frank Robinson said. "We wanted him to go down there and stay sharp. If something happens, we told him that we would get him back up here. It's a good insurance policy."
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.