Matt Cain progressing, but still has a ways to go

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HOUSTON — Matt Cain continues to progress in his rehab, throwing 30 pitches off a bullpen mound Friday and awaiting his next session Tuesday.

Cain isn’t close to returning to the Giants’ rotation — he hasn’t thrown breaking pitches and won’t face hitters anytime soon — and might not be activated until July. The Giants aren’t providing a timetable, but Cain is considering one.

“I’d love to say before the All-Star break, but I don’t know,” he said. “We’ll see how that goes. I think that could be achievable. It might not. It’s just something I thought of, sitting down looking at it on paper with (trainer Dave Groeschner). It might be just after the break. I can’t really say.”

Cain continues to build up arm strength as he recovers from a flexor-tendon strain near his right elbow that shelved him just before the season. He had elbow surgery in the offseason to clean up bone chips but doesn’t feel his elbow being “heated up” as it was in his rehab from surgery.

In Cain’s place, Chris Heston has posted a 2.91 ERA in seven starts and is coming off a two-hitter in which he struck out 10, issued no walks and retired the final 22 batters.

“I’m really impressed with his composure and the way he’s been able to go about his business between starts,” Cain said. “He throws a complete game after having a little bit of a struggle the game before. That shows his maturity. That’s huge. That’s what you need out of a young starter.”

Briefly: A day after Tim Lincecum twice fell while making pitches, manager Bruce Bochy said the Giants should have asked the Great American Ball Park’s grounds crew to better stabilize the mound. ... On Star Wars Night at the yard, Bochy revealed his favorite character: Chewbacca, fittingly.

John Shea is a San Francisco Chronicle staff writer.

On deck

Saturday

at Reds

4:10 p.m. CSNBA

Vogelsong (1-2) vs. Leake (2-1)

Sunday

at Reds

10:10 a.m. CSNBA

Heston (3-3) vs. DeSclafani (2-3)

Monday

Off

Leading off

Local angle: Cincinnati manager Bryan Price, who grew up in Mill Valley, has a 4-foot-by-3-foot framed picture of Mount Tamalpais in his office with Richardson Bay in the foreground.

— John Shea