Left-handed starting pitcher Sammy Solis, rated as the Nationals’ 10th best prospect by Baseball Prospectus, will undergo Tommy John ligament-replacement surgery next Tuesday in Los Angeles, General Manager Mike Rizzo said.

 Solis complained of soreness in his left elbow Friday after a bullpen session Friday. Team physician Dr. Wiemi Douoguih administered tests on Solis afterward and expressed his belief Solis had torn the ulterior cruciate ligament in his left elbow. Today, Solis traveled to Los Angeles for a second opinion from Dr. Lewis Yocum.

 “Unfortunately,” Rizzo said, “we had bad news today.”

Solis first experienced elbow discomfort last December after an impressive performance in the prospect-laden Arizona Fall League. At that point, the Nationals put Solis through physical tests to determine if he needed Tommy John surgery and gave him an MRI. The MRI showed a possible, but passed the physical tests. Douoguih then recommended Tommy John surgery, but a second opinion differed.

 Because Solis passed the physical tests, the Nationals followed a plan to rest him for a month and then let him build arm strength slowly at their accelerated minor league camp. Solis had thrown multiple side sessions before he injured himself Friday.

 “I thought we had dodged a bullet there,” Rizzo said. “We always knew that this was a possibility. We felt that instead of cutting on him right away, we felt maybe we could through this with rehabilitation. And we couldn’t. It cost us a couple of months. We felt if two doctors weren’t 100 percent sure that Tommy John is needed, I wasn’t going to be the one to say it was needed.”

 The Nationals drafted Solis, 23, in the second round in 2010 out the University of San Diego and gave him a $1 million signing bonus. Last year, after starting the season late because of a groin injury, Solis pitched 96 2/3 innings between Class A Hagerstown and Class A Potomac, going 8-3 with a 3.26 ERA and a 4.04 strikeout-to-walk ratio.

 Solis would have likely begun this season at Class AA Harrisburg, and may have challenged for a spot in the Nationals rotation as soon as 2013. Instead, if all goes well, Solis will be back to full strength by the middle of next spring training.

.“He’s a terrific prospect,” Rizzo said. “We always thought, even after we drafted him, he was a quick-to-the-big leagues guy. This will derail that a little bit. But we feel confident he should regain his pre-injury form and we feel that once he does, he’ll be a definite positive factor for us.”