ALLENTOWN, Pa. -- Two veteran ballplayers looking to return to the big leagues will make their debuts on Friday for the Phillies' Triple-A affiliate, Lehigh Valley.

Former Major League All-Star Jason Marquis will make his second Minor League start in his attempted return from Tommy John surgery, while three-time big league All-Star Grady Sizemore is expected to start in center field. Marquis was signed as a free agent earlier this month, while Sizemore was inked to a Minor League deal after being cut last week by the Red Sox.

For Marquis, the opportunity is one that even he didn't expect to have this soon in the rehab process. Less than 12 months removed from undergoing his Tommy John procedure, Marquis is looking to build off an impressive outing Saturday for the Phillies' Gulf Coast League affiliate.

Marquis tossed five shutout innings, while striking out seven batters before moving over to a practive field to throw another two innings in a simulated game. He fired 90 pitches in all and, most importantly, suffered no setbacks along the way.

"I'm assuming they liked what they saw and that's why they let me come up here so soon and try pitching at a higher level," Marquis said. "I'm excited about the opportunity and we'll see what happens."

Lehigh Valley manager Dave Brundage said he doesn't have an exact pitch limit for Marquis yet, but said that he doesn't expect significant restrictions. As for Marquis, he said he's prepared to pitch "until they come take the ball from me."

"Knowing what he's gone through and coming off the surgery, just being ahead of schedule is encouraging in itself," Brundage said. "I don't have any huge expectations for him -- we don't want to load up his plate with too much at this point. We just want him to get back to feeling strong and feeling like himself."

Given the normal soreness and routine he has gone through in the four days since his last start, Marquis said he's not worried about any lingering effects from the surgery. Though he knows he still has a ways to go before finding his way back into a Major League rotation, the 14-year veteran is hopeful that the worst is behind him.

"Throughout this whole process, it seems like it's been nothing but improvement," Marquis said. "I've been very fortunate and I haven't really had much drama. It's been a smooth recovery so far and I'm hoping it stays that way."

Last season, Marquis raced out to a 9-2 start with a 3.63 ERA through his first 14 starts with the Padres. It quickly unraveled for him, however, as the right-hander then went 0-3 with a 5.13 mark over his final six starts leading up to the season-ending surgery. For his career, he sports a 121-114 record over 368 big league appearances (309 starts) with eight different teams.

For now, he finds himself working his way back through the Minors, hoping to once again reach the big leagues with what would be his ninth team in 15 seasons. The next step comes Friday night at Coca Cola Park against Minnesota's affiliate, the Rochester Red Wings.

Marquis admitted that he's excited to face tougher competition, but said he's happy just to be pitching on any mound at this point in his recovery -- and his career.

"It didn't really matter to me that it was 18-year-old kids or Dominican prospects or whoever it was that first time out there. I was just excited about getting on the mound," Marquis said. "I still had those little jitters. That's how I've always approached it. It's something that I love to do and I care about it, so I'll always have that little edge when I step on the mound."