OAKLAND -- Mitch Spence envisioned himself finally getting a shot to pitch in a big league rotation this season when the A’s selected him first overall last December in the Rule 5 Draft. After all, starting is all he’d done for most of his Minor League career in the Yankees’ organization.

The A’s were on board with giving Spence a chance to earn a rotation spot upon drafting him. As the offseason went along, though, that plan shifted. The additions of veterans Alex Wood and Ross Stripling pushed Spence down Oakland’s depth chart, leading to him making the Opening Day roster as a relief pitcher.

It took a couple of months and a few injuries to the rotation, but that starting opportunity is starting to materialize for Spence. Making his fourth Major League start in Tuesday night’s 4-3 loss to the Mariners at the Coliseum, Spence turned in his longest outing yet, going six innings and allowing four runs on nine hits and one walk with three strikeouts.

The final line was not as crisp as Spence’s previous outing, which saw him take a no-hitter into the sixth and finish with 5 1/3 scoreless frames in a win over the Rays last week. In some ways, though, the rookie’s start on Tuesday was arguably just as impressive for the mettle he showed on the mound.

After keeping Seattle off the board his first time through the order, Spence ran into trouble his second time through in the third when the top of the lineup hit four doubles and scored three runs in the span of five batters.

The second and third time facing an opposing lineup can often spell doom for a young pitcher, especially one with as little big league experience as Spence. Instead, he was able to limit the damage and get better as the night went along. Spence finished his outing by retiring six of his final seven batters faced and held Seattle’s offense to 2-for-9 his third time through the order.

"Spence did a good job,” said A’s manager Mark Kotsay. “This is part of that process of maturing. For Mitch, pitching in that long role, he generally got through a lineup once. Now he’s seeing lineups twice and a third time, which you’ve got to mix your pitches well and keep hitters guessing to keep them off balance. … He manages the game pretty well."

While beginning the season in the bullpen was not Spence’s desired outcome, he embraced the role and developed a routine that helped him stay ready for whenever that call to warm up might come. He also adjusted his mentality to focus on staying in attack mode on the mound, knowing that he could enter games in tight situations.

Spence might not be in the bullpen anymore, but that mentality remains the same.

"In the bullpen, you come in and you can just let it rip because you only have one or two innings,” Spence said. “Here, you have to pull back the reins a little bit. But the mentality of attacking guys is still one that I keep."

Since moving into the rotation on May 17, Spence has taken advantage of his opportunity. He’s posted a 3.32 ERA through four starts with six walks and 15 strikeouts in 19 innings. His five-pitch mix -- cutter, slider, curveball, sinker, changeup -- has always suggested he has enough in his arsenal to compete in a big league rotation. With injured starters Wood, Stripling, Paul Blackburn and Joe Boyle still at least a few weeks away from returning, Spence is earning an extended look as a starter, just as he hoped for.

"I’ve just been trying to take it in stride,” Spence said of the opportunity to start again. “I’ve started in the past, so I just lean back on the routine that I’ve had. The biggest thing is with the pitch count going up, I’m making sure I get in the training room and get my recovery in so I can stay on the field."