MESA, Ariz. -- The weather heating up in Arizona over the past week is symbolic of the current state of the A’s rotation battle.

Coming into camp, manager Mark Kotsay indicated that a six-man rotation was an option that has been internally discussed, largely hinging on how newcomer Shintaro Fujinami adjusts to an every-fifth-day role. To this point, the expectation is that Oakland will open the season with a traditional pitching staff of five starters and eight relievers, though one of those bullpen slots could be a multi-inning role filled by one of the starting pitchers who does not make the rotation.

Of the 10 pitchers in camp who classify as legitimate rotation candidates, seven have now pitched in at least two Cactus League games. Adam Oller improved his case in Thursday’s 1-0 victory over the Dodgers at Hohokam Stadium with arguably the best outing of any A’s pitcher yet, tossing four scoreless innings with two hits and two walks while striking out seven.

“I love the competition,” Oller said. “I think it’s good for everybody. You bring good competition in, it’s either going to bring the best out of you or you’ll crumble. I feel like we’ve all brought the best out of each other. It’s been a lot of fun.”

At roughly the halfway point of Spring Training, here’s a look at where the starting rotation picture stands:

Locks: Paul Blackburn, Shintaro Fujinami, Drew Rucinski
Blackburn is coming off an All-Star campaign and is likely the favorite to take the mound for the A’s come Opening Day on March 30 at the Oakland Coliseum. Fujinami has matched the hype that came with his signing this offseason by flashing electric stuff through his first two spring outings, with the only question being how his arm bounces back on a normal workload. His second Cactus League outing came five days after his first, but the A’s expect to test out how he responds to four days of rest soon.

A signal that Rucinski’s spot on the starting staff might be secure came Thursday, when the A’s opted to have him face hitters in a sim game at their Minor League complex to build up his workload rather than have him pitch in a Cactus League game.

In the mix: Adam Oller, Ken Waldichuk, Kyle Muller, Adrián Martínez
Oller continues to find success with his recently added breaking ball. Of his seven punchouts against the Dodgers on Thursday, five were finished off on the breaker, which he describes as somewhat of a hybrid between a slider and a curveball. Through three Cactus League outings, Oller holds a 1.86 ERA and leads all pitchers on the roster with 14 strikeouts in 9 2/3 innings.

Waldichuk (Oakland’s No. 2 prospect) has struggled to reach his targeted innings number due to high pitch counts over his first two starts, allowing five runs on five hits and four walks over 2 2/3 innings. Muller (No. 5) has had mixed results over three outings, most recently going 3 2/3 innings and allowing two runs on five hits and one walk with three strikeouts in an exhibition game against Team Colombia.

Martínez looked sharp before leaving camp to join Team Mexico in the World Baseball Classic, going four innings without allowing an earned run in his two spring games. The A’s will keep an eye on how he performs in the Classic over the next couple of weeks.

Starter/bullpen options: JP Sears, Freddy Tarnok
Sears pitched solely as a starter upon joining the A’s in the Frankie Montas deal last season, but his experience as a swingman during his time with the Yankees makes him an ideal candidate to provide long relief should he not come away from camp with a rotation slot.

Tarnok (No. 9) is more likely to begin the season at Triple-A Las Vegas, but his performance early in spring should keep him on the radar. He’s allowed just one earned run in three outings, including Wednesday’s exhibition against Colombia.

Unknown: James Kaprielian
Easing into Spring Training as he returns from offseason shoulder right surgery, Kaprielian has been facing hitters in live batting practice and simulated action but has yet to appear in a game this spring. Kotsay maintains his belief that there is enough time left for him to build up into a full starters’ workload, especially with the number of off-days the A’s have at the start of the season. A better outlook for Kaprielian should come once he makes his Cactus League debut.