CINCINNATI -- A college student who caught Sammy Sosa's 500th home run baseball considered giving it to him, but has decided to keep it and find out what it's worth.

Bonds sends his congrats

Barry Bonds told reporters covering the Giants-Brewers game Saturday in Milwaukee that he was happy to see Sammy Sosa had joined him in the 500-homer club. "Sammy may have one of those years," Bonds told reporters Saturday. "Once you hit the 500 barrier -- boom! -- it might relax him enough that he might hit 80 home runs this year. Next minute, you know, Sammy is at 600 in the blink of an eye. This is his time, his year." Sosa hit the mark with a seventh-inning homer Friday night in Cincinnati. "I'm pretty sure he wanted to do it at [Wrigley Field], but you want to get that out of the way as soon as you can. Now he will be able to relax. I'm proud of him. I hope he's proud of himself. Anybody would be." Sosa is 12 homers from tying Ernie Banks' Cubs record of 512 home runs. Bonds has 614, fourth on the all-time list. -- ESPN.com news services

Zach Kirk was sitting in the right-field stands with his girlfriend Friday night when Sosa hit a seventh-inning homer that deflected off several sets of hands and came to rest at his feet.

Kirk, 22, of St. Louis, is a Cardinals fan and thought about how a member of the grounds crew returned Mark McGwire's 62nd home run ball to him after he broke the single-season record in 1998.

"It crossed my mind to give it back," Kirk said Sunday. "At the same time, I'm 22 and a senior in college. It could be a blessing.

"I'm going to keep it and try to sell it."

Kirk is a general studies major at Missouri and plans to become a high school teacher and soccer coach. He had not received any offers or contacted any memorabilia dealers or auction houses to get an idea of the ball's value.

The ball would go "definitely for five figures, and it could be six figures," said Julie Stoklosa, a spokeswoman for Internet auction house MastroNet.

"It depends on the popularity of the player, if the player is popular with collectors," Stoklosa said Sunday. "Sammy Sosa is."

Kirk had never caught a ball at a game before Friday night, when he went to the Reds' game at the urging of his girlfriend, who lives in suburban Cincinnati and attends Miami University in nearby Oxford.

"The closest I came was at Wrigley Field, when a ball bounced in front of me," he said.

His girlfriend suggested they get tickets to the Reds game so they could see Great American Ball Park, which opened this week. Sosa's 500th homer wasn't on their minds.

Sosa came to Cincinnati one home run shy of the mark after failing to hit one during a three-game series against the Mets.

"It was all her idea," he said. "She was the one who picked up the tickets and picked out the seats in right field, hoping Adam

Dunn or Ken Griffey Jr. would hit a home run there."

Kirk said Sosa's homer flew over their heads, then bounced down.

"It landed at my feet, and I just dove on it," he said.