Philadelphia Phillies first baseman Bryce Harper was prescribed rest for his ailing back and anticipates rejoining the lineup Friday.

Harper sat out Monday for the fourth consecutive spring training game with soreness in his lower back. He left the game Thursday against the Boston Red Sox and has zero home runs and no RBIs this spring.

Given his back issues in the past, Harper is aware of outside concern about his availability early in the season. He said he "overdid it" and will be ready for Opening Day on March 28 against the Atlanta Braves.

"I feel pretty confident. I'm fine," he said.

Harper said he discussed slowing his workload to be prepared to play the opener with Phillies manager Rob Thomson, whose greater concern for Harper was having him get work at first base as he transitions from the outfield.

"When I talked to Thomper, when I told him I was a little sore, he was like, 'All right, we'll just throw you down a little bit and pick you back up next week. We'll see where you're at,'" Harper said. "I said, 'If it's back field or big field, I'll get my at-bats.'"

Harper, 31, played in 126 games last year as he returned from Tommy John surgery and hit .293 with 21 home runs and 72 RBIs.