The 24-year-old right-hander threw eight scoreless innings on Friday night during a rehab start for Double-A Carolina against Tennessee.

"I felt good, everything felt good," Johnson said. "I felt strong. Even into the eighth, I felt like I could go out there one or two more innings."

Recovering from Tommy John ligament replacement surgery he underwent last Aug. 3, Johnson likely will join the Marlins and start either next Wednesday in San Diego or on Thursday in Los Angeles.

Before the Marlins faced the Rockies on Friday night, manager Fredi Gonzalez noted that if all went well for Johnson, he could join Florida on their current road trip.

Johnson responded with a big effort in his fifth rehab assignment, his third at the Double-A level.

In eight innings on Friday, Johnson allowed five hits and struck out seven with two walks. He also helped himself at the plate, belting a home run.

It was Johnson's second home run during his rehab assignment. He also went deep while pitching for Class A Jupiter.

"I kind of figured he would throw me a curve, but I don't know what happened," he said. "I thought I'd strike out every time. After that I thought, 'OK, that wasn't too bad, maybe I'll get a couple more hits.'"

In all, Johnson threw 28 1/3 innings in his rehab stint. He also went back-to-back games throwing more than 100 pitches. He threw 111 pitches on Friday.

"I'm in the best shape of my life right now," Johnson said. "I think my comeback last year, that was the most frustrating. [The disabled list] was what I needed to do, though, to get everything healthy."

Johnson, who finished fourth in the NL Rookie of the Year voting in 2006, last pitched for the Marlins on July 4, 2007 against the Padres in San Diego. In that game, he exited after five innings with forearm tightness.

When the Marlins activate Johnson, they will decide whether to use him on July 9 or July 10. Scott Olsen also is in line to start on July 9.