OAKLAND -- While Mark Ellis and Landon Powell are teammates on the field, the pair partook in a friendly rivalry off of it.

Ellis, who played college ball at the University of Florida, and Powell, who attended South Carolina, had a bit of a wager going on as their two former schools duked it out in the College World Series -- but neither would reveal the specifics of the bet, other than that it was "high stakes."

"My family wouldn't be ashamed of me," Powell said before Tuesday's home game against the Marlins. "It's not like I'm going to lose the house or anything, but we both are rooting for our team to win. It should be fun."

Powell said he still needed to talk trash to Ellis after South Carolina eked out a win in an extra-innings affair in Game 1 of the best-of-three championship series. And the trash talking will surely continue after the Gamecocks completed the sweep with a 5-2 win Tuesday night in Omaha, Neb.

Despite his team winning back-to-back championships, Powell admitted that he thought Florida was probably the better team this year -- something Ellis wholeheartedly agreed with. The A's longest tenured player was confident that his team would come back from the early loss and come away with the school's first CWS title, but the Gators fell short of that distinction, and now Ellis will have to pay up on the bet.

This isn't the first wager Powell has had during the CWS this year, either, as several of the teams involved in this year's tournament were well represented inside Oakland's clubhouse. Conor Jackson, Tyson Ross and manager Bob Melvin all spent time at Cal, and Cliff Pennington -- the victim of Powell's earlier bet -- attended Texas A&M.

"A lot of the guys in this clubhouse went to college; it's kind of the Oakland A's way," Powell said. "We all had good experiences in college, and we still root for our teams."

Balfour placed on DL with right oblique strain

OAKLAND -- Grant Balfour's right oblique strain has resulted in something that the dependable righty hoped to avoid: a trip to the disabled list.

The A's placed Balfour on the 15-day disabled list on Tuesday, retroactive to June 22, because of the injury, which has kept Balfour unavailable out of the bullpen since the team's series in Philadelphia over the weekend.

"Grant really isn't a guy that can ease into things," A's manager Bob Melvin said. "He's a full-out, max effort guy and a guy who is very important to us. We don't want to go down that road where we can potentially reinjure this thing.

"Oblique injuries can be tricky things, so we want to make sure that when he comes back he's fully healthy."

The decision to place Balfour on the disabled list came after the righty underwent an MRI that showed the soreness to be more than what the team expected. Balfour had the MRI because when he was throwing in Philadelphia, he felt that he couldn't throw beyond "50 to 60 percent" without feeling like he would worsen the injury.

"It's disappointing, for sure," Balfour said. "I felt great, my arm feels great and my body feels great. It's just one part of me right now that's a little sore and I need to get that fixed up. It's frustrating."

For Balfour, it's his sixth career stint on the DL, and it couldn't come at a worse time for the reliable setup man. Balfour is having a solid season out of the bullpen, and is in contention to represent Oakland in the All-Star Game.

The righty was tied for second among American League relievers with four wins at the time he was placed on the disabled list. He is 4-1 with two saves and a 2.48 ERA. In 33 appearances, opponents are hitting just .198 against him, including .136 with runners in scoring position. He has also not allowed a run in nine of his last 10 outings.

Despite the stellar stats, the oblique strain could hurt Balfour's chances of being named an All-Star for the first time in his career, but he hopes to be back before the All-Star break.

"If [being an All-Star] is something that was going to happen, hopefully it does," Balfour said. "I feel like I've had a few decent years where I've had a chance to make it, and I definitely would hate to see this jeopardize something like that. I got no control over that, I just have to get myself healthy and pitch for the team. Making an All-Star team would be awesome, but I have a team here that I need to worry about."

To replace Balfour, the A's recalled right-hander Trystan Magnuson to add a long reliever to the bullpen. It is Magnuson's second stint with the A's this year. During his first run, Magnuson made two appearances, pitching three innings and giving up six runs.

Melvin shuffles rotation with Harden on way

OAKLAND -- A's manager Bob Melvin shuffled the team's rotation on Tuesday prior to the start of the A's nine-game homestand, paving the way for righty Rich Harden to make his first appearance of the season.

Melvin moved righty Guillermo Moscoso into the starting spot for Wednesday's game against the Marlins, relegating fellow rookie Graham Godfrey to bullpen duties. The shuffle means that righty Trevor Cahill's next start will be in Thursday's series finale, and it sets up Harden for his Oakland debut on Friday against Arizona.

Harden has been sidelined all season with a right lat muscle strain after signing a one-year, $1.5 million contract with the A's, but has made two rehab starts with Triple-A Sacramento in his quest to come back from the injury. During his time in Sacramento, he pitched 7 2/3 innings, allowing three runs with 12 strikeouts and three walks.

Harden was scheduled to make one last rehab start to get his pitch count up higher, but Melvin and the A's decided against it.

"We felt like at 90 [pitches], we can keep him," Melvin said. "That's a good number for us. We want him healthy, and he is healthy right now. The people that have the eyes on him feel like he was throwing well at this point. Rather than send him out one more time and get him to 110, we're comfortable with where he's been at this point."

Part of what played into the decision to forego a third rehab start for Harden is Godfrey's performance since being called up. The righty is 1-1 with a 4.24 ERA in three starts but has allowed just three earned runs in his last two appearances.

The shift means that Godfrey will add another long-relief option to an already stout bullpen, and Melvin said that the rookie could conceivably give the team up to 100 pitches in relief. Although he is used to being a starter, Godfrey isn't completely unfamiliar in a bullpen role, having spent about two weeks there last season in the Minors before returning to the rotation.

Despite being relegated to the bullpen, Godfrey is taking the move in stride.

"I feel fine," he said. "I'm still glad to be a part of the team. Even though it's a new role, I'm going to try to do the best that I can and try to contribute and help the team win."

Worth noting

• Brandon McCarthy, who has been sidelined with a stress reaction in his throwing shoulder, was scheduled to make a rehab start on Tuesday in Stockton, but it was rained out. The righty will instead take the mound Wednesday for the Class A Ports.

A's manager Bob Melvin hinted that he tentatively has McCarthy scheduled to make his return to the club sometime over the weekend, but that could change.

• The A's announced on Tuesday that the team agreed to terms with three more players selected in this month's First-Year Player Draft, including Fresno State outfielder Dusty Robinson, the team's 10th-round selection. The team also agreed to terms with 33rd-round pick Austin Booker, who helped guide Cal to an appearance in the College World Series, as well as 39th-round pick Shane Boras, who is the son of agent Scott Boras.

The club has now signed or agreed to terms with 25 of its selections, including 18 of its first 25 picks.