PORT CHARLOTTE, Fla. -- Finding flaws in David Price is a difficult proposition, but the Rays would like to see him refine his changeup.

Price has a 97-mph fastball and a knee-buckling slider, and once he has the changeup totally down, Tampa Bay feels he will have command of three above-average pitches, which would qualify him to be a top-of-the-rotation starter.

A changeup is one of the toughest pitches to hit, and it is equally difficult for pitchers to master.

"It's a pretty tough pitch, just because of the fact you have to be able to repeat the same delivery, the same arm action, the same everything as your fastball," said Rays starter James Shields, whose best pitch is the changeup. "To be able to do that is tough. And you have to have the right grip, and a grip that feels comfortable to each individual."

Shields almost sounded like an inventor when he talked about how his changeup -- a two-seam circle change -- came to him.

"I was messing around with my brother one day -- he was a left-handed pitcher in college and he had a really good changeup -- and he kind of just showed me his grip, and we kind of messed around with it a little bit," Shields said. "I asked him which was the best one, and I ended up just refining it a little bit."

Eureka!

Given the success of his changeup, Shields is often asked how he grips the pitch.

"I've shown people my grip and they can't throw it," Shields said. "It works for me. But like I said, everybody is different."

Shields, whose locker is next to Price's in the Charlotte County Sports Complex, said he worked some with Price on his changeup last season, but has not done so this spring.

"It's actually coming along pretty well," Shields said. "He just needs to keep throwing it. The more you throw it, the better off he's going to be. He's already got a pretty good changeup -- he just needs to throw it."

Price said he has found a grip he likes -- the popular circle change grip.

"Now I just need to keep doing what I've been doing," Price said. "It has gotten tons better. Repetition with a changeup is how you make it better. What I've been doing is throwing it a ton. I'll just keep working on it."

Shields said he has been happy to help Price.

"He's a good guy -- anything I can do to help our staff," Shields said. "Of course, he can't teach me how to throw 97 [mph]. We need an even trade here."