A’s: How Oakland’s post-break rotation is shaping up.

Oakland’s rotation coming out of the break isn’t set in stone, manager Bob Melvin said Sunday, but Edwin Jackson looks a good bet to start Friday against the Giants and Trevor Cahill and Sean Manaea also are likely to start in that three-game series.

When he was sent down to Triple-A Nashville on Tuesday, the plan was for pitcher Frankie Montas to return July 24 at Texas, which means that Brett Anderson is penciled in for the previous night’s game against the Rangers. Daniel Mengden will be available at Triple-A Nashville when needed, but Oakland’s front office likes to be flexible, which means younger players with options left get sent down to make way for those who would have to clear waivers if designated for assignment.

That said, Anderson’s 6.08 ERA puts him in a precarious situation. Another poor start or two, and he could be heading out now that Mengden has recovered from a sprained foot and is off the disabled list.

Injury update: Melvin said that starter Daniel Gossett (elbow strain) is throwing at a distance of 90 feet, and outfielder Matt Joyce received an epidural injection for his sore back.

Saturday “was the first day he’s started to feel pretty good,” Melvin said. “He’s not doing any baseball activity yet, but hopefully we’re turning the corner with how he feels overall.”

Party like it’s 1989: Next weekend will feature a number of events to honor the A’s 1989 championship team, including autograph sessions and fireworks on Friday, a pregame ceremony Saturday, and on Sunday, the giveaway will be Rickey Henderson “BobbleLegs.”

Henderson will throw out the first pitch that day on the playing surface named for him.

Briefly: The A’s will not work out during the break; they’ll have a workout before Friday’s game at the Coliseum . ... AllStars Jed Lowrie and Blake Treinen were scheduled to take a red-eye flight to Washington after Sunday’s game; they were to land about 5 a.m.