BALTIMORE -- Right-hander Jason Hammel reported to the Orioles clubhouse on Saturday following six scoreless innings in Friday's start against the Royals with minimum discomfort in his right knee, a nagging issue which has progressively gotten better.

"Each time out he's had less residual than the time before," manager Buck Showalter said of Hammel, who had his start skipped earlier this month, but has managed to avoid the disabled list. "So far, so good. He said he's just a little sore."

Hammel had his right knee drained earlier in the week and posted his longest outing in nearly three weeks, holding the Royals in check with seven strikeouts.

"I was aware of the knee, in the fifth inning was when it started," he said following the Orioles' 8-2 win. "I knew it was there, maybe a little bothersome. But then I got through the sixth with the same feeling. So it didn't get any worse. So huge, huge step there. So in between this start and the next one we'll continue to build strength, and hopefully we got over a nice hurdle."

Hammel, who said previously that he felt as if he were pitching "on one leg" at times, has been able to incorporate elliptical training into his between-starts regime and he felt the cardio helped his stamina Friday night. He has also been doing pool work in place of running to help keep the weight off of his knee.

"The body can deteriorate after a while if you're not doing anything to maintain stamina and endurance," said Hammel, who is 6-1 with a 2.78 ERA in nine starts. "Just being able to do something I think really helped and we are going to stick with it."

Roberts getting work with O's affiliates

BALTIMORE -- Orioles second baseman Brian Roberts, who played in his first rehab game on Wednesday, continues to progress back from a concussion that has sidelined him more than a year. Roberts is working toward his activation date on June 12.

Roberts played three consecutive rehab games at second base and took Saturday off. He will play again for Double-A Bowie on Sunday and Monday, with the plan to increase from two to three plate appearances. Roberts will head to the O's affiliate in Delmarva and play Tuesday and Wednesday, when the Baysox hit the road.

O's manager Buck Showalter said the plan is for Roberts to get four at-bats for the Shorebirds.

"The way he's got it drawn it up, he'd have the equivalent of Spring Training under his belt at-bats-wise, be in the mid-50s plate appearances [at the end of his rehab]," Showalter said. "So he's doing probably more work before the game, playing two or three innings."

Showalter, who was on hand for one of Roberts' games, said the other reports have been good and the biggest challenge for the veteran infielder is adjusting back to game speed.

Asked if he had discussed headfirst sliding with Roberts, a facet of his game that Roberts has admitted he may have to adjust, Showalter said: "We haven't gotten there yet. [I'll] kind of believe that when I see it. I think he's going to play the game with some energy. That's one thing, the couple games I saw his clock isn't quite there ... he'll get there."

Tidbits

• Bill Hall, who was designated for assignment on Friday, cleared waivers and was outrighted to Triple-A Norfolk.

• Lefty Zach Britton gave up two unearned runs in five innings on three hits with three walks and six strikeouts in his first rehab start for Double-A Bowie on Saturday. Outfielder Endy Chavez and third baseman Mark Reynolds also were scheduled to play. Britton threw 88 pitches, 56 for strikes.

• Orioles top pitching prospect Dylan Bundy was set to make his first start Saturday night since being promoted to Class A Advanced Frederick. The 19-year-old Bundy did not allowed an earned run in the first 30 innings of his professional career.