"I look at the bright side," Rizzo said. "Tommy John surgery is a surgery that we've had great success at. The success rate for guys coming back from Tommy John and retaining their stuff is very good."
Strasburg was pulled from Saturday's game at Philadelphia when he grimaced and shook his wrist after throwing a changeup.
The Nationals initially called the injury a strained flexor tendon in the forearm, but an MRI taken Sunday raised enough questions for the Nationals to order a more extensive MRI in which dye is injected into the arm.
The No. 1 overall pick in the 2009 draft, Strasburg struck out 14 batters in a sensational major league debut in June. He is 5-3 with a 2.91 ERA and 92 strikeouts in 68 innings.
But he has had medical setbacks along the way, despite the team's best efforts to be as cautious as possible with their prized youngster. He was placed on the disabled list a month ago with inflammation in the back of his right shoulder. He was making his third start since returning from the DL when he had to leave the game against Philadelphia.
"The player was developed and cared for in the correct way, and things like this happen," Rizzo said. "Pitchers break down, pitchers get hurt and we certainly are not second-guessing ourselves. ... Frustrated? Yes. But second-guessing ourselves? No."