TORONTO -- Brian Roberts has started working out again in Florida as he continues to recover from concussion-like symptoms.

The second baseman has been progressing through an upper-body exercise plan that was developed by concussion specialist Dr. Michael Collins. Roberts hasn't reported any ill effects as he has progressed through the plan.

"He's starting to do some more physical things down there," Orioles manager Buck Showalter said. "He's gotten into an exertional program. He's doing light upper-body exercises. He's moving along good."

Roberts hasn't seen the field since May 16 at Fenway Park, when he started getting headaches after a headfirst slide into first base. Up until this point, the concussion-like symptoms had limited Roberts from undergoing most physical activity as he slowly progressed through his rehabilitation.

The team isn't taking any chances with the veteran infielder, who has battled injury in the past. The concussion-like nature of this injury gives the Orioles even more reason to not rush anything with Roberts.

"We already have progressed really slowly and done it the way that the doctors have prescribed," Showalter said. "It's not something that you try to get on a different timetable. You go with the people that are experts at it, and you work within their time frame."

This is the second straight season that Roberts has been bothered with a long-term injury; he missed 59 games in 2010 with a herniated disk in his lower back. The 33-year-old also battled back and neck injuries this Spring Training after another headfirst slide into first base.

For now, the team is hoping that Roberts will be cleared to resume baseball activities on June 21.

Tidbits

• Mark Reynolds was back in the lineup at third base and hitting eighth for the Orioles on Tuesday night after leaving Sunday's game after the seventh inning with a left forearm contusion. Reynolds said he was still sore but felt game-ready and would have been fine to play if the team had a game Monday.

• First baseman Derrek Lee also returned to the lineup Tuesday night after missing the team's weekend series in Tampa Bay while attending his grandfather's funeral in Sacramento. First baseman Brandon Snyder was optioned to Triple-A Norfolk to make room for Lee.

• Cesar Izturis reported to extended spring training Tuesday, where he will continue to rehab from surgery he had on his right elbow to repair nerve irritation. Manager Buck Showalter said Izturis had moved on to "the next step" as far as improving his range of motion and participating in rehab exercises.

• Right-hander Justin Duchscherer will throw 4-5 innings Thursday in the last game of extended spring training. He has yet to pitch this season because of a lower back injury.