SAN DIEGO -- One day shy of the six-week anniversary of surgery on his left shoulder, Padres reliever Joe Thatcher took what he considered a pretty significant step forward in is rehabilitation by playing catch for five minutes at PETCO Park on Sunday.

"I'm excited to get out there and do something baseball related," Thatcher said. "This [not playing] has been real boring."

Thatcher had surgery on May 2 to shave down his frayed labrum and rotator cuff and to remove the bursa sac in his left shoulder.

Thatcher was placed on the 15-day disabled list on March 29, retroactive to March 22.

A year ago, Thatcher was one of the top left-handed specialists in the National League, posting a 1.29 ERA in 65 games.

Bass coming up to replace injured Harang

SAN DIEGO -- The Padres will purchase the contract of 23-year-old right-handed pitcher Anthony Bass on Monday and immediately give him a start against the Rockies at Coors Field.

Bass is needed because the Padres will place Aaron Harang on the 15-day disabled list on Monday with a right foot contusion, an injury that goes back to a start on June 4 against the Astros.

Harang won his seventh game of the season Thursday, limiting the Astros to two runs in six innings but did so under considerable duress.

"He pitched in extreme pain," Padres manager Bud Black said.

Bass, a 23-year-old right-hander, is a combined 7-3 with a 3.41 ERA in 12 starts in 2011 between Double-A San Antonio and Triple-A Tucson. Opposing hitters are batting .244 against him this season and he has 60 strikeouts in 63 2/3 innings.

"He's been throwing well, throwing strikes with good velocity and a good, hard breaking pitch," Black said.

Bass, who was drafted in the fifth round in 2008 out of Wayne State University, appeared in four games in Spring Training.

"There's some familiarity with all of us," Black said.

As for Harang -- who is 7-3 with a 3.71 ERA in 13 starts in his first season pitching in his native San Diego -- the pain his foot got to be difficult to deal with. He had an X-ray on Thursday that came back negative.

"It's in the top, and I mean, it radiates through the foot every time I hit when I go to take off running," Harang said. "It kind of sends a quick shock through my foot."

With Monday's starter figured out, the Padres will now turn their attention to figuring out who will start Tuesday in Colorado.

Dustin Moseley dislocated his left (non-throwing) shoulder on a swing Wednesday, and the Padres aren't sure if he'll be ready to go.

"The Moseley situation is still in flux," Black said. "That start is in jeopardy."

The Padres could move left-hander Cory Luebke into the rotation for Moseley, although they would be short of their designated long reliever in the bullpen if they do. The team could promote left-hander Wade LeBlanc from Tucson.

LeBlanc is scheduled to make his next start Monday in Reno.

Frieri sees results as arm soreness subsides

SAN DIEGO -- Padres reliever Ernesto Frieri pitched a shutout inning in each of the first two games against the Nationals this series, recording two strikeouts in each appearance.

In his two previous appearances, Frieri gave up a combined three runs in one inning.

San Diego manager Bud Black said after Friday's game that the true version of his right-hander is the more recent performance.

"We've seen Ernesto's stuff, from the first of the year to where it is now, improve as far as velocity and the sharpness to his breaking pitches," Black said. "He's not invincible, but it's good to see him throwing the ball.

"With velocity, we saw a couple of pitches 94 miles per hour, which I think is probably the high-end for him, but we didn't see that much in April."

Frieri's velocity was down at the start of the year, usually topping out in the low 90s or high 80s.

"I mean I didn't feel that good at the beginning of the season," Frieri said. "There was something, my arm wasn't ready at all. Pretty much every time I pitched, I felt really sore."

The 25-year-old said that he felt that soreness in his arm during his follow-through and that it hampered him throughout April.

"My control wasn't that good, because I didn't know where the ball was going to go, and my velocity was really low, too," Frieri said. "I was throwing low 90s, 88, 89 miles per hour. And, wow, I was like, 'Oh my God, what's going on?'

Frieri never got an answer to that question. The soreness just went away. He hopes that it stays that way, especially with Luke Gregerson on the disabled list with an oblique strain.

"I think I've got my velocity back and my fastball movement, so that's why I'm getting people out," said Frieri, who has a 2.53 ERA in 29 appearances. "I feel great. I feel really, really good right now."