Thompson supplanted Gross as batting coach in 2004 and has been part of consecutive National League championship teams the past two years.
But the Phillies, still missing injured slugger Chase Utley, have slipped offensively this season. After a 2-0 victory in 11 innings against St. Louis on Thursday they are 49-46 and seven games behind first-place Atlanta in the NL East.
The 57-year-old Gross has been a coach for Triple-A Lehigh Valley the past three seasons and served as the Phillies' major league batting coach from 2002-04.
He played 10 years for the Phillies (1979-88) and reached two World Series.
Moyer placed on DL; rotation set
Philadelphia Phillies pitcher Jamie Moyer is headed for the 15-day disabled list with an elbow injury that forced him out of his last start after only one inning.
The 47-year-old left-hander was hurt Tuesday and general manager Ruben Amaro Jr. said he had a sprained ulnar collateral ligament and a strain of the flexor pronator. Amaro said Moyer would be out indefinitely, but the team hadn't determined whether he'd require reconstructive surgery.
Kyle Kendrick, optioned to Triple-A Lehigh Valley after surrendering three homers in one inning in his last start, will be recalled and pitch in his regular spot on Saturday.
The Phillies plan on recalling left-hander J.A. Happ to replace Moyer on Sunday.
