"It just locked up on him," Cash said after the game. "I don't think anyone has a real explanation. I think he feels a little bit better."
Forsythe had five home runs in the past nine games, including a long two-run shot on Monday night. The severity of the back spasms is unknown. On the season, he's hitting .280 with 15 home runs and 38 RBIs.
Forsythe has been in the lineup every game since returning from the disabled list on June 10.
Sam Blum is a reporter for MLB.com based in Tampa. This story was not subject to the approval of Major League Baseball or its clubs.