Much like they did en route to 97 wins and a postseason appearance last year, the A’s will rely heavily on a deep bullpen to help mask rotation concerns in 2019.

The A’s used 15 starters in 2018, and 11 made seven or more starts, tied for most in Major League history, amid a slew of injuries. Already this year, they’ve been tested again, robbed of top prospect Jesus Luzardo (shoulder) for at least two months.

A trio of veteran starters will be counted on to carry the bulk of the load: the A’s need innings, and lots of them, from Mike Fiers, Marco Estrada and Brett Anderson. Health will be key for this group, particularly Estrada, who pitched through back issues for much of 2018.

When healthy, eating up innings is what Estrada does best. Prior to an injury-plagued 2018, when he totaled 143 2/3 innings, the right-hander completed at least 176 in three straight seasons and averaged a 3.88 ERA.

Fiers, meanwhile, worked 172 innings between Detroit and Oakland last year, while Anderson was able to provide only 80 1/3 innings following his May promotion in between a pair of injury list stints.

Beyond them, the A’s are counting on a pair of out-of-options pitchers, Frankie Montas and Aaron Brooks, to provide innings from the back end; and they’re not discounting the use of an opener in front of one or both from time to time.

Right-hander Liam Hendriks is up for the task after handling these duties in September last year. He also started the American League Wild Card Game in this role, when the A’s turned to their bullpen rather than throwing a traditional starter against the Yankees.

“This is going to be the strength of the season, the bullpen,” Hendriks said. “We’re going to ride it all the way.”

Hendriks will be one of eight relievers in a bullpen headlined by closer Blake Treinen and setup men Lou Trivino and Joakim Soria. The A’s also have Fernando Rodney at their disposal and a lone lefty in Ryan Buchter. Each piece will be essential to getting 27 outs 162 times.

This much was clear in their first two regular-season games in Tokyo; Fiers lasted just three innings in Wednesday's 9-7 loss to Seattle, while Estrada went five in the next day's 5-4, 12-inning loss. That meant plenty of work for the relief corps, which should be a season-long trend. Whether it’s sustainable is unclear.

“You obviously want to see your starters go deep in the game,” A’s manager Bob Melvin said, “but we’ve also seen that just doesn’t always happen, and our guys have done a good job of building a deep bullpen that we’re going to have to use a lot.”