DETROIT -- Jason Hammel, recovering from surgery on his right knee, will throw a bullpen session on Saturday under the watchful eye of pitching coach Rick Adair, and the plan is for him to attempt more pitches than he did on Wednesday but at the same level of effort.

"The original injury, when I threw the pitch in the game that time, it hurt [behind the knee]," Hammel said. "So it's obviously dealing with getting past that, because it's still a little tentative to push off of it. But the first 'pen I threw was like 70 percent, second 'pen was about 90 percent. So a little more effort, and I was a little more sore that last time. But [that's] to be expected when you're putting more effort into it."

Hammel, 29, and the Orioles are still targeting a return in early September, with the next step throwing in a simulated game.

"That's obviously the next step from throwing in a bullpen, but who knows?" said manager Buck Showalter, who was careful not to put an exact timetable on Hammel's return. "It could be two or three times more down there [in the bullpen].

"I'm going to leave it up to Rick and [head athletic trainer Richie Bancells] and Ham, because they're aware of each other and what he needs to do. But so far, so good. If you had told me when the surgery happened that we would be sitting here this close to talking about [his return], I'd feel real good about it."

Hammel, who has a 8-6 record and 3.54 ERA, was placed on the 15-day disabled list on July 15. He had pitched well despite dealing with the nagging soreness in the knee that finally forced him to undergo surgery. His return is expected to help stabilize an inconsistent rotation, and he has made no secret about the fact that the rehab process can't go quickly enough.

"It actually feels great walking on it, just that movement off the mound is the only thing we have to get by," he said. "I think if I can get through that, we can be off and running."

Britton to start vs. Tigers on Saturday

DETROIT -- Left-hander Zach Britton joined the club in Detroit on Friday, and although the club hadn't officially ruled out using right-hander Steve Johnson, it was determined after the series-opening 5-3 loss that Britton will get the start on Saturday.

Johnson threw 28 pitches over two innings to end Thursday night's game and was available out of the bullpen again on Friday, though he was not used.

"He handled last night real well, I thought," manager Buck Showalter said on Friday of Johnson, who had seven days off in between outings. "So, you know, I want to be fair to Steve, too. ... Because even if he got through tonight and [I] didn't use him, how far can you expect to use him [on Saturday]? You want some length there."

Asked if the Tigers are more vulnerable to left-handed pitching, Showalter said, "They are not susceptible to anything. They are good. No, I know [Friday starter Tommy Hunter has] had a good outing against them and I know Zach struggled in an outing here last year, but our need supersedes that right now -- for a starting pitcher. I wish we didn't have to use Stevie last night. We didn't have any choice."

Britton made his first start on Thursday since being optioned to Triple-A and allowed six earned runs over 3 2/3 innings. He cracked the nail on his left index finger and struggled with command and finishing his pitches before being removed in the fourth inning.

"I think sometimes you put too much pressure on yourself to compete and you forget about executing pitches," said Britton who has gone 1-1 with an 8.10 ERA in five Major League starts. "That's really what I need to do now. I can't worry about, 'My ERA is here. I need to get it down here.' I need to take it pitch by pitch. It's a long season and it's a tight race, so I know I have to compete just like everyone else is doing on the team."

Britton struggled after being recalled from Triple-A Norfolk the first time, posting just one quality start in five tries. The 24-year-old lefty started the season on the disabled list with an injury to his left shoulder, and it took him a while to regain his stuff and command.

"It's just a process," he said. "[Showalter and pitching coach Rick Adair are] giving me a chance to see if it all comes around this outing. But it's good to know they see the progress. They're not just looking at the numbers. Sometimes I'm looking at the numbers and thinking, 'What the heck?' and I have these guys telling me, 'You know what? You're coming through something, and we see the signs of you getting back to where you used to be.' Hopefully, I can put it together for the rest of the season."

Worth noting

• Wilson Betemit took a cortisone injection in his sore right wrist on Thursday and has headed to the team's spring facility in Sarasota, Fla., as expected.

• Reliever Stu Pomeranz, on the disabled list with a strained left oblique, has been slowed with a back injury as well. Pomeranz received a cortisone injection in Sarasota on Friday to help speed the treatment.

• Troy Patton has reported to the team's spring facility as well and is getting treatment on his right ankle.

• Despite playing just 118 games, the Orioles have made 132 roster moves since setting their Opening Day roster.