PEORIA, Ariz. -- The Padres have a week left to set their season-opening rotation, and by now, the basics of that race are fairly straightforward.

Yu Darvish and Joe Musgrove are at the top. They're the two starters who are fully built up and could pitch on Opening Day. Mike Clevinger and Blake Snell are also in the rotation, though both will enter the year with some form of workload limitations.

The battle at the back end of the rotation is headlined by Nick Martínez, Chris Paddack, MacKenzie Gore and Ryan Weathers. Martínez was brilliant on Wednesday, pitching four scoreless innings in the Padres' 4-2 victory over Milwaukee at Peoria Stadium. He struck out four, while allowing two hits and a walk.

“We’re just going out there and pitching,” Martínez said of the rotation race. “We’ll leave that decision up to the guys above us.”

But here's the thing about the Padres' rotation race: Even to the decision-makers, it's not entirely clear just how many places will be available. And it's not entirely clear whether those places are starting roles, or if there’s room for a piggyback out of the bullpen.

“It changes every day,” said manager Bob Melvin. “I’m still leaning toward five. But you probably also have to look at who can give you innings? … There are just a lot of things we’re continuing to think about.”

Here’s a look at the three scenarios the Padres are weighing -- why each one might happen, why it might not and a projection of what each rotation would look like:

A regular five-man rotation

Why it might happen: Melvin has made it clear that this is his preference. Even with Clevinger and Snell on workload restrictions, the Padres have plenty of cover for their leftover innings. With rosters reportedly expanding to 28 players for April, that almost certainly means the Padres will employ a 10-man bullpen.

Why it might not: Even with the extra roster space, the first two weeks of the season will be a grind. The Padres open the year with 14 games in 14 days. It seems likely that they'll settle into a five-man rotation as the season wears on. But with a taxing start to the year, the Padres won't want to burden their pitchers too much, too early.

Projection:

1. Darvish
2. Musgrove
3. Clevinger
4. Martínez or Paddack
5. Snell

A five-man rotation with piggyback(s)

Why it might happen: If the Padres want innings, this is the safest way to find them. Clevinger and Snell will be limited, but if one (or both) of them is followed by another starting pitcher, their start days won't end up being a burden on the rest of the Padres' pitching staff. Plus, the Padres can piggyback pitchers of different handedness on top of those two, potentially giving them matchup advantages. Thursday’s Cactus League game against the D-backs might even serve as a preview. The lefty Snell is slated to start, with the righty Paddack to follow. It’s entirely possible the Padres use that model early in the regular season as well.

Why it might not: The Padres have other options for length in their bullpen -- say, Nabil Crismatt or Dinelson Lamet (or even Weathers in a more flexible relief role). If they’re carrying 10 relievers, there should be plenty of arms to cover for Clevinger and Snell. On top of that, there might be value in getting Weathers, Gore and perhaps even Paddack on a starter's schedule in the Minors, with all three viewed as long-term starting options.

Projection:

1. Darvish
2. Musgrove
3. Clevinger, then Weathers
4. Martínez
5. Snell, then Paddack

A six-man rotation

Why it might happen: It might only last two weeks. But a six-man rotation could be the best way for the Padres to limit the wear and tear on their starting pitchers coming out of an abbreviated camp. If they carry nine relievers, that's almost certainly enough to cover the relief innings -- even if a few of their starters aren't pitching all that deep into games. In theory, the Padres would then slide back to a five-man rotation in late April, as soon as the off-days start piling up.

Why it might not: As noted, it's not Melvin's preference, and for good reason. Melvin noted the rhythm pitchers find when they work every fifth day -- a rhythm they've grown accustomed to for most of their careers. Plus, the quicker you turn over a rotation, the quicker you get back to your best pitchers at the top. By definition, a five-man rotation means more innings for your better pitchers.

Projection:

1. Darvish
2. Musgrove
3. Clevinger
4. Martínez
5. Paddack
6. Snell