PEORIA, Ariz. -- Manny Machado took some ground balls on Saturday, as he went through his first full workout in Padres camp. Every single ground ball came at third base.

That's no surprise. The Padres and Machado have made it very clear he'll be a third baseman exclusively in San Diego.

But until Saturday, before the Padres' 6-4 win over the Mariners at Peoria Sports Complex, it was at least worth wondering whether there's some scenario in which Machado might get time at short. The Padres, after all, have a number of fringe third basemen in camp, and top shortstop prospect Fernando Tatis Jr. probably won't be called up for a month or two.

Manager Andy Green erased any doubt.

"I don't think we have any anticipation of putting him anywhere besides third base," Green said. "Every game comes with a caveat that injuries occur and things happen. ... But we have no anticipation of that happening for us. We have anticipated him locking down third base for the foreseeable future."

On the surface, Green's answer seems a bit redundant given what's been said over the past few days. But it actually cleared up a few questions about the roster.

As things stand, the Padres have at least one -- and probably two -- backup infield places available. Earlier this week, Ty France, Jason Vosler and Seth Mejias-Brean were all bona fide contenders. All three play first and third base.

Well, Eric Hosmer's at first. Machado's at third. And the Padres have other options for both spots in case of emergency. Suddenly, it's hard to see a place for any of those three on the Opening Day roster -- unless they absolutely rake this spring and win a job as a pinch-hit threat.

Meanwhile, Greg Garcia, Jose Pirela and Esteban Quiroz -- once third-base candidates themselves -- are in pretty good shape, because of their ability to play second (and, in Garcia’s case, short).

Infield candidates star in opener

The Padres beat Seattle in their Cactus League opener on Saturday, 6-4. The aforementioned infield competition took center stage.

Pirela opened the scoring for the Padres after leading off the second with an opposite-field double off Felix Hernandez. An inning later, Pirela singled up the middle on a tricky slider from Cory Gearrin. It was a nice start for the much-maligned utility man, who slumped to a .645 OPS last season.

He was replaced by Quiroz in the fifth inning. The Padres landed Quiroz in November in the trade that sent Colten Brewer to Boston. He's an intriguing option, who spent his first seven professional seasons in the Mexican League, before posting a .283/.406/.547 slash line in the Red Sox organization last year.

In his first at-bat as a Padre, Quiroz smacked a single up the middle. He also reached base in the seventh with a sharp grounder to second that produced an error.

Ultimately, Quiroz and Pirela might find themselves fighting for the final place on the roster this spring. Garcia -- who went 1-for-2 on Saturday -- seems like a heavy roster favorite, given that he can play short, and he’s a platoon option for Luis Urías and Ian Kinsler.

"We don’t know how the middle of our infield is going to play out," Green said. "Ian Kinsler is probably the front-runner to be at second base to start the year. But we’ll see how [the rest] plays out."

Mitchell back in action

Bryan Mitchell's quest for a place in the rotation got off to a shaky start. He surrendered a long home run to Mariners leadoff man Shed Long with the third pitch he threw.

From there, however, Mitchell settled in nicely, inducing a few swings and misses with his refined breaking ball. He worked two innings of one-run ball with one strikeout.

A year ago, Mitchell was handed a place in the rotation at the start of camp, but he slumped to a 5.42 ERA in 16 appearances during the regular season. He saved himself a place in the organization's plans with a strong September. But he's got work to do if he hopes to make the big league club.

"We all know the spot I’m in," Mitchell said. "Y'all do. I do. I’m taking my starts like I’ve got six tests to go out there and show what I want to do."