The Cincinnati Reds have traded Ken Griffey Jr. to the Chicago White Sox.
Griffey Jr., 38, is hitting .245 with 15 home runs and 45 runs batted in over 102 games this season, his ninth with the Reds.
The right-fielder in June became just the sixth man in baseball history to reach 600 career home runs.
As a major-leaguer with more than 10 years of experience and more than five years with the same club, Griffey Jr. had the ability to veto the trade, but he agreed to head back to the American League, where he began his career in 1989.
"I spoke with Ken, and he is excited to be coming to Chicago to try to help us reach the post-season," said Chicago general manager Ken Williams.
Cincinnati receives right-handed pitcher Nick Masset and minor league infielder Danny Richar, both in their mid-20s. Masset had appeared in 32 games with the White Sox, as a middle reliever.
"Ultimately, I think it's going to really open up my future as a starter," Masset told MLB.com. "I'm really looking forward to being a starter, if that's where they want me to fit. That's something I always wanted to do, and I'm excited to head over to the National League."
Under manager Ozzie Guillen, Chicago (60-46) began Thursday 1½ games ahead of Minnesota in the AL Central division.
"Ozzie has the opportunity to field his best team, offensively and defensively, on a day-to-day basis over the next two months," said Williams. "And this gives us a chance to keep some of our middle-of-the-order hitters fresh and producing down the stretch.
Griffey Jr. has not appeared in the playoffs since 1997, the same year he was named the AL most valuable player when he was with the Seattle Mariners.
For his career, Griffey Jr. has 608 home runs with 1,754 RBIs and a .288 batting average.
He is in the final year of a nine-year contract that includes a team option to retain him for $16.5 million US next season.