By now Yankees manager Joe Girardi has plenty of experience dealing with players not available to him. And that list grows daily.

Though David Robertson’s left hamstring problem near the back of the knee isn’t serious — at least not yet — enough to put the right-handed reliever on the disabled list, the Yankees don’t expect to have the eighth-inning arm until at least Tuesday when they open a three-game series against the Rockies in Denver.

“My guess is that we will get him in Colorado,’’ Joe Girardi said before Friday night’s 2-0 loss to the A’s at Yankee Stadium for which he didn’t have Joba Chamberlain (DL) and Robertson available. “He will be out for a few days here and hopefully it heals up.’’

Robertson said he felt something in the area when he broke to cover first base Wednesday night.

“It’s a little sore but it feels better,’’ said Robertson, who hoped to be available Saturday but that was before Girardi said he pitcher won’t work until Tuesday.

Chamberlain was the 10th Yankee to land on the DL this year when a right oblique muscle barked while he warmed up in the bullpen Tuesday night.

So, without Chamberlain and Robertson, Girardi was down to Shawn Kelley, Adam Warren, Vidal Nuno and Preston Claiborne, who was elevated from Triple-A Scranton-Wilkes Barre.

Kelley and Warren, right-handers, have been with the Yankees all season but neither has pitched in high-pressure situations. Claiborne, a right-hander, impressed in spring training but has never thrown a pitch to a big league batter in the regular season. Nuno, a lefty, made his major league debut Monday with three scoreless innings against the Astros.

Last night Warren replaced CC Sabathia after six innings and threw three scoreless frames.