Brad Mills has a 7.76 ERA in 15 big league appearances.

OAKLAND -- Lefty Brad Mills, dealt to the A's from the Brewers for all of 100 pennies on Tuesday, will start in place of the injured Drew Pomeranz on Friday night vs. the Red Sox.

Jesse Chavez, originally scheduled to go Friday, has been pushed to Saturday.

Mills was in the A's clubhouse Thursday afternoon and worked out with the club pregame, but he won't officially be added to the active roster until Friday, at which point Oakland will make a corresponding roster move.

The $1 price tag was a technicality of a clause in Mills' Minor League contract with the Brewers that included an out if he was not in the Majors by June 15. Milwaukee was forced to make his availability known to other teams and let him go if one wanted him.

The A's did.

Of the $1 fee, Mills smiled and said, "I thought it was a joke. Whatever they had to do to make it official, I'm all for. I don't take it as a value of my worth as a ballplayer."

The 29-year-old, who has a 7.76 ERA in 15 big league appearances, including 10 starts, was 4-2 with a 1.56 ERA in 14 appearances (12 starts) at Triple-A Nashville this season, including one stretch of 18 1/3 scoreless innings.

Now he's prepping to make a start for a team with the Majors' best record.

"I did read that last night," Mills said, "but you wouldn't know it. First impression here, it's just like anywhere else. There's no pressure, it's just baseball. First and foremost, my goal is to contribute and be a part of it.

"Obviously they're playing really good baseball and they pitch really well. It's fun. You feed off of that. It's fun when you're feeding off each other. It's not a competition, you're trying to hold your own with everyone on the staff, and I think that's a good vibe to have."

Worth noting

• Lefty Eric O'Flaherty needed just eight pitches -- all fastballs -- in a perfect inning of relief for Triple-A Sacramento on Wednesday, marking his fourth rehab appearance and third with the River Cats.

Nearing the end of Tommy John surgery rehab, O'Flaherty is expected to pitch in five or six more Minor League games before joining the A's active roster. Manager Bob Melvin says the southpaw's velocity has been consistent around 90-91 mph.

• In the same game, rehabbing outfielder Josh Reddick (hyperextended right knee) started in right field while going 1-for-3 at the plate and "felt good running the bases," said Melvin.

Reddick, who will play at least four games with the River Cats, also went 1-for-3 with a double and a walk in Thursday's game.