OAKLAND -- Coming off a herculean effort in the opening series of the regular season against the Angels, the A’s bullpen may have to take a backseat in the club's two-game series against the Rockies that opened Tuesday.

A’s relievers helped the club win three of four against the Angels, allowing just one earned run, and limited the Halos to a .157 average over 20 1/3 innings over the series. But that heavy workload came at a price, as A's manager Bob Melvin said “several” relief pitchers will not be available for Tuesday night’s series opener against Colorado.

“We’ve used our bullpen a lot. That’s what happens when you use multiple guys three out of four days,” Melvin said. “It’s something that, when you’re in close games and your starters aren’t going long, that ends up happening.”

Which relievers are down Tuesday? Melvin didn't specify, but it’s likely Burch Smith, Jake Diekman, Yusmeiro Petit and Joakim Soria will get a rest. Smith tossed two scoreless innings on Monday, while Diekman, Petit and Soria entered Tuesday having pitched in each of the previous two games.

Who might be available? Lou Trivino is one of the fresh arms in the bullpen, with his only appearance being a scoreless inning in Saturday’s 4-1 loss, while J.B. Wendelken has only thrown a third of an inning. Liam Hendriks was given a planned day off Monday and will be ready for closer duties again on Tuesday.

Another option out of the 'pen is Jordan Weems, who has not yet pitched this season and could make his Major League debut against Colorado.

A much-needed rest will come for the entire club on Thursday, as the A’s are off before heading to Seattle for four-game series with the Mariners beginning Friday. Also helping is that after Daniel Mengden made his first start of the season on Tuesday, all starters will have gone one turn through the rotation. It is expected that A’s starters will be on more of a regular workload of up to around 90 pitches in their second starts of the season, beginning with Frankie Montas on Wednesday.

“All of us want to go out there and throw five, six, seven innings,” Montas said. “We’re all ready to go more pitches than we did in our first start so I think we’ll go deeper in the games now.”