Wilson tore the anterior cruciate ligament in his knee Saturday night in Washington's 2-1 victory against Cincinnati at Great American Ball Park. He suffered the injury in the seventh inning as he chased after a ball that had ricocheted off his glove on a pitch from Jordan Zimmermann.
"He'll have to be operated on," said Johnson Sunday morning. "He'll be out most of the year. I don't know the severity of it, if it's just the ACL or if there are other complications, but we'll find out."
Ramos was officially placed on the 15-day disabled list Sunday, and Jesus Flores will take over as the everyday catcher. The Nationals called up Sandy Leon from Double-A Harrisburg to take Ramos' spot on the roster. Entering Sunday, Flores had started nine games this season and was hitting .200 with four RBIs.
Flores has fought back from his own share of severe injuries. A left ankle sprain cost him the final 22 games in 2008. A right shoulder bruise/fracture and partially torn right labrum limited him to just 29 games in '09, and he missed the entire '10 season rehabbing from surgery to repair his right labrum.
"It's not the way that I want to be in [the lineup]," said Flores. "But from the other side, I've just been really patient the last couple of years, working hard and preparing myself to look for that chance to play every day. I want to show that I can be that everyday player like I was in the past. It's meaningful for me and my career."
Leon, who will wear No. 41 with Washington in Sunday's series finale against Cincinnati, batted .319 with 10 doubles, one homer and 12 RBIs in 27 games this season with the Harrisburg Senators. The 23-year-old has thrown out 41 percent (12 of 29) would-be basestealers in 2012 and has caught 133 of 261 (51 percent) runners over the past three seasons. Leon has batted .246 with 11 home runs and 137 RBIs during six Minor League seasons.
Ramos becomes the ninth player currently on the DL for Washington, including five who have been out for the the first 33 games this season. Outfielders Michael Morse and Jayson Werth, and reliever Drew Storen are among key players the Nationals are playing without.
"We're going to have to start eating bananas or something to change our luck," said Johnson. "We've had more than our fair share of key players go down. ... [Ramos] will be sorely missed, as Jayson Werth has, as Michael Morse has and Storen. But we've got some quality players and we'll survive."
Kevin Goheen is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.