PHOENIX -- The D-backs all but set their Opening Day roster Sunday, with only a lone bullpen spot remaining and manager Torey Lovullo announcing what was widely assumed -- Madison Bumgarner will start Thursday's opener against the Padres in San Diego.

Bumgarner, who was signed to a five-year, $85 million free-agent deal prior to last season, also started Arizona's opener in 2020, which was also at Petco Park.

The left-hander went 1-4 with a 6.48 ERA in nine starts in 2020, but he put together back-to-back strong starts to finish the year and the organization is confident he will bounce back now that he's had a normal Spring Training. Last year, Bumgarner struggled to regain velocity on his fastball after the pandemic shut down baseball for three months.

"Obviously, a well-deserved honor that he's done many, many times," Lovullo said. "And I know he's excited by it. It was something I talked to him about post-outing the other day. And, you know, it's Opening Day, I know that he's going to be proud to take the mound for the Arizona Diamondbacks on that day."

The rest of the starting rotation will lay out as follows: Merrill Kelly, Caleb Smith, Taylor Widener and Luke Weaver.

Here's a look at how the rest of the roster is shaping up.

Catchers (2): Carson Kelly, Stephen Vogt
No surprises here.

Infielders (7): Nick Ahmed, Asdrúbal Cabrera, Eduardo Escobar, Wyatt Mathisen, Josh Rojas, Josh VanMeter, Christian Walker
Essentially, both VanMeter and Mathisen made it over Trayce Thompson, who can play all three outfield positions. Thompson, who was reassigned to Minor League camp on Sunday, had a hot start at the plate this spring, but he cooled off as it went on.

Rojas played extremely well this spring and should see a lot of playing time at second base to open the year. He'll also serve as the backup to Ahmed at shortstop.

Outfielders (4): Tim Locastro, Ketel Marte, David Peralta, Pavin Smith
Kole Calhoun (right knee) will start the year on the injured list, though he is not expected to miss much time.

Smith played his way onto the team and can play all three outfield spots, as well as first base, and the D-backs also have some infielders -- Rojas, Mathisen and VanMeter -- who can play the corners.

Rotation (5): Madison Bumgarner, Merrill Kelly, Caleb Smith, Taylor Widener, Luke Weaver
Widener takes the place of Zac Gallen, who will start the year on the injured list with a hairline fracture in his right forearm. The decision essentially came down to Widener or Taylor Clarke, with Widener getting the nod for the rotation and Clarke making the team as a reliever.

"[Widener] has been throwing the ball very, very well," Lovullo said. "I think we were looking for somebody that could step in there and give us a very capable outing, and Taylor certainly deserves that opportunity."

Bullpen (8): Joakim Soria, Stefan Crichton, Alex Young, Taylor Clarke, Kevin Ginkel, Chris Devenski, Yoan López, TBD
Devenski pitched outstanding this spring and has appeared to claim a spot as a non-roster invitee, though nothing has been made official of yet.

Tyler Clippard sprained his right shoulder capsule last week, which opened a spot in the bullpen that the team has yet to fill. The D-backs could recall a player they already optioned to Triple-A Reno, such as J.B. Bukauskas or Riley Smith, or they could look to claim or sign a player off waivers before Thursday.

"The final piece of this puzzle, for me, is somebody who can go up there, compete and get outs, and do whatever is going be necessary to help us win a baseball game," Lovullo said.