SAN DIEGO -- The Padres finalized their 25-man roster Sunday morning, deciding on No. 6 prospect Colin Rea for their final rotation spot and choosing Adam Rosales and Ryan Buchter for the final bench and bullpen roles, respectively.
In the wake of the final roster decisions, left-hander Robbie Erlin, outfielder Jose Pirela and infielder Alexi Amarista were optioned to El Paso. Utility man Jemile Weeks, who entered camp on a Minor League deal, will also begin the season in Triple-A.
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Here's a position-by-position breakdown of the Padres' roster decisions:
Rotation:Tyson Ross, James Shields, Andrew Cashner, Drew Pomeranz, Rea
Ross, Shields and Cashner will start the club's three games against the Dodgers this week -- in that order -- but it remains unclear who will start Friday in Colorado.
Manager Andy Green has said he wouldn't use Thursday's off-day to tinker with the rotation, meaning some combination of Pomeranz and Rea will start Friday and Saturday against the Rockies.
Rea, who beat out Erlin for the final rotation spot, had a bit of an up-and-down spring, posting a 5.73 ERA and a 1.73 WHIP. Still, the club likes his increased fastball velocity, and he looked very good at times during Cactus League play.
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Bullpen:Fernando Rodney, Brandon Maurer, Kevin Quackenbush, Matt Thornton, Carlos Villanueva, Buchter, Luis Perdomo
With Pomeranz -- who was a favorite for the bullpen at the start of camp -- in the rotation, Buchter figures to serve as a valuable left-handed arm out of the 'pen -- along with the veteran Thornton.
The club initially indicated that right-hander Josh Martin, a Rule 5 Draft pick, would make the Opening Day roster. But a few hours after announcing the 25-man squad, Martin was designated for assignment in what general manager A.J. Preller called "an administrative move."
Rule 5 Draft selections must remain on the Major League roster for the entirety of the season or be offered back to their original club -- in this case, the Indians -- after clearing waivers. By putting Martin on the roster and designating him, the club essentially gained itself 10 extra days to find a way to keep Martin in the organization -- perhaps with a trade.
"We'll probably have some conversation with Cleveland if it gets to that point, see about trying to keep him in the organization," Preller said. "But he's really kind of in limbo right now."
The club has not yet mapped out its plan for the bullpen ahead of closer Rodney. Quackenbush and Maurer would figure to serve mostly in a setup role.
Catcher:Derek Norris, Christian Bethancourt
The Padres performed better at catcher this spring than any other position, with Norris, Bethancourt and Austin Hedges all hitting above .300 and playing solid defense.

With Norris ingrained as the starter, the club decided to begin the season with Hedges at Triple-A, where he will get routine at-bats.
"He's earned a Major League roster spot," Green said. "He's earned the opportunity to be here. It's just not yet. It's not a never. It's: Your day's coming, go play every day, keep getting better, keep progressing, and you're going to be a huge part of what we do going forth in the future."
Infield:Wil Myers, Cory Spangenberg, Alexei Ramirez, Yangervis Solarte, Brett Wallace, Rosales
Rosales, who entered camp on a Minor League deal, had his contract selected when the club DFA'd Martin. He homered four times in the final five games this spring -- including Thursday's game against El Paso -- batted .283/.365/.522 and played all four infield positions.
"The versatility, the ability to play all over the field," Preller said. "He showed in Spring Training all four infield spots. I think Andy felt good about him being able to bounce around the infield. [He's] a right-handed bat, and he obviously comes with a lot of energy every day."
Rosales, who isn't much of a speed threat, beat out Weeks and Amarista for the super-utility role. He probably got a boost with the inclusion of outfielder Travis Jankowski, who will serve as the primary pinch-runner.
Weeks, meanwhile, batted .340/.407/.585 and played six defensive spots, including all three outfield positions. He and Amarista will begin the season in Triple-A, but Green reiterated on Saturday that the big league roster is fluid.
"April 4 is big to everybody because it's fun," he said. "But it's not the defining moment of the season."
Meanwhile, Wallace, who battled a right foot injury earlier in camp, is fully healthy and will serve as the backup first baseman and the primary pinch-hitter against righties.
Outfield:Matt Kemp, Jon Jay, Melvin Upton Jr., Jabari Blash, Jankowski
The Padres set their five outfielders on Saturday, with Blash and Jankowski coming off the bench.
The decision to put two outfield-only types on the bench was something of a small surprise. But Jankowski and Blash (another Rule 5 Draft pick) offer precisely opposite skill sets, so it makes sense.
Jankowski is a speed threat and a premium defender who hits from the left side. Blash, meanwhile, has prodigious right-handed power, but he struggles with strikeouts and has work to do defensively.