BOSTON — When Brad Penny's fastball starts creeping up to 96 and 97 mph, good things happen. Lately, Penny has been hitting that rarified territory regularly, the first stretch that he's consistently boasted that kind of velocity since 2007.

It shows on the mound. Over the past month, Penny has been extremely effective, allowing just seven earned runs his last five starts, in 28 2/3 innings for a 2.20 ERA. It's no coincidence that over that stretch, his average fastball velocity has been just under 95 mph, after sitting below 93 for the first two months of the season.

Finding that velocity again has allowed Penny to once again become the true power pitcher who cruised through the National League in 2006 and 2007.

"I've always pitched with velocity, all of my career," he said. "I think that health is the key, being healthy after last year, that's why I'm pitching well."

In 2006 and 2007, Penny's fastball velocity was tops in the National League, averaging over 93 mph. Last year, his shoulder started to trouble him, and his velocity fell off a cliff. In some months he could hit the mid 90s — and others, he was lucky to break 89.

Penny visited the disabled list three times last year because of shoulder tendinitis. When he signed with the Sox, he did it partly to join their vaunted shoulder strengthening program. It's a decision that has paid off for both sides. Without the program, he's not sure if he would even still be in the majors.

"All of it," he said of how much the program has to do with his success. "Yeah, like I've said, if I wasn't here, I don't know if I'd be pitching."

The improvement has been gradual. Penny touched 95 for the first time in his final spring training appearance, but the velocity wasn't consistent.

With his fastball still in the lower 90s, Penny labored through April, keeping the team in games but never really dominating.

Penny spent much of May and early June as the subject of persistent trade rumors, as many wondered whether he would be the one to go when the team cleared a rotation spot for John Smoltz.

With the rumors swirling, Penny pitched his best ball of the season, looking like a different pitcher from the man who took the mound in April.

"My whole career, there have been trade rumors," he shrugged. "I can't control any of that, so I've just got to go out there and pitch."

Now, with Daisuke Matsuzaka on the disabled list and Penny looking sharp, the Sox are likely relieved they didn't pull the trigger on any of the rumored deals floating around.

Penny's fastball was strong on Saturday, sitting between 95 and 97 most of the game. He used it to set up his changeup and curveball, and located it effectively. His fastball was his out pitch for four of his six strikeouts.

Manager Terry Francona said Penny's effectiveness goes back further than just this recent stretch.

"He'll give you a chance to win every time out. I'd say it's much more than [the last] five [starts]. All but about two starts this year he's been pretty solid," Francona said.

Jason Varitek has caught Penny all year and has seen the consistent improvement. He expects more to come as the pitcher becomes more comfortable with his body and his newfound health.

"Through time he's going to get even better," said Varitek. "He's strong. He's given us quality start after quality start."

dbarbari@projo.com