WASHINGTON – Nationals first baseman Nick Johnson will undergo surgery Tuesday on his injured right wrist and may not return this season.

“We'll know more tomorrow when they operate, but there's a possibility he might be out for the year,” Nationals general manager Jim Bowden said before Monday night's game against the Angels.

Johnson has been on the disabled list since May 15 with a tear in the tendon sheath of his right wrist. He was sent to the Mayo Clinic for more tests Monday to determine why the injury has taken so long to heal. The team announced hand and wrist specialist Dr. Richard Berger recommended a diagnostic arthroscopy to evaluate the ligaments on the ulnar side of Johnson's wrist.

Johnson will undergo the procedure Tuesday at the Mayo Clinic.

“They're going to go ahead and look and see what it is, and then we'll know more,” said Bowden, who declined to offer a best-case scenario.

Johnson has been prone to injury throughout his career, and missed the entire 2007 season while recovering from a broken leg. He was hitting .220 with five home runs and 20 RBIs in 38 games before the injury.