DUNEDIN, Fla. - Ken Giles walked off the mound Tuesday afternoon alongside a Phillies trainer. The tightness in his back had returned. His outing was finished after just two batters.

Giles spent the next half hour in the trainer's room of the visitors clubhouse at Florida Auto Exchange Stadium.

"Just tightness. It's just stiff," Giles said. "It doesn't hurt. I'm able to move around. I'm not really concerned about it."

Giles, 24, said he expected to be ready for opening day. It is possible that the Phillies will use caution and start their promising reliever on the disabled list. Giles does not expect to have a hard time convincing the team that he is healthy.

"I don't think they'll be too pushy on that because they know I'll speak the truth," Giles said. "Every day they always want to know how I'm feeling and stuff like that, but I'm not really concerned about that kind of stuff."

The righthander said he has felt tightness for a few days in the middle of the back. He kept the muscles loose with exercises and thought the feeling went away before Tuesday's game.

"Once I got back out there and tried to rev it up, it kind of just clenched up," Giles said.

Manager Ryne Sandberg said Giles would be evaluated by a doctor Tuesday night. He said he was not sure whether the back had attributed to Giles' dip in velocity this spring. His fastball reached 95 m.p.h. Tuesday, his highest mark of the spring.

The pitcher routinely reached 100 m.p.h. last season with an average speed of 97.2, according to FanGraphs. Giles mixed the pitch with an effective slider to compile one of the best rookie seasons in team history. He struck out 64 batters in 452/3 innings.

Giles said his fastball is just where it needs to be this spring.

"I don't want to be too in shape when I go in the season, then when the season goes on I kind of wear down," Giles said. "So around where I'm at right now I think it's going to be perfect. Then I can just continue to build up during the season."

Giles, Jake Diekman, and Justin De Fratus are expected to be the bridge to closer Jonathan Papelbon. All three have followed last year's breakout seasons with periods of inconsistency. Giles has struck out 10 batters in 82/3 innings but has walked two batters in three separate outings.

@matt_breen