PEORIA, Ariz. -- The Padres' season-opening rotation is falling into place. It’s not exactly the one they envisioned all offseason. It’s not too far off, either.

Clarity arrived Friday, when the team named Blake Snell its Opening Day starter. Further clarity arrived Saturday when manager Bob Melvin noted that, yes, Joe Musgrove is bound to open the season on the injured list, and, yes, it’s fair to read into the current alignment of the rotation.

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Snell pitched Friday. Nick Martinez faced the Rangers on Saturday. The Padres round out their Cactus League slate with Michael Wacha on Sunday and Seth Lugo on Monday.

That would line up this rotation for the Padres’ season-opening six-game homestand:

1. Blake Snell
2. Nick Martinez
3. Michael Wacha
4. Seth Lugo
5. TBD
6. Yu Darvish

Aside from Snell, none of those probables is etched in stone. But that's currently the Padres' plan, at least.

Snell might have earned an Opening Day nod anyway. But in an ideal world, Darvish and Musgrove would have been options, too. Instead, Darvish is still building up after an irregular schedule at the World Baseball Classic, and Musgrove is recovering from a fractured left big toe.

Here's a look at what's left for the Padres' remaining rotation pieces to fall into place:

Darvish's buildup
Darvish won't appear in a Cactus League game this spring after he spent February training with Team Japan. He made two relief appearances in the knockout rounds of the Classic, and he only returned to camp on Thursday.

The Padres aren't too concerned with Darvish's readiness, considering he's a 36-year-old veteran who was practically fully built up before the Classic. But they'd still like to get him a couple of outings before the regular season.

On Saturday, Darvish was slated to pitch a Minor League game at the Peoria Sports Complex. His next outing would presumably come on Thursday -- meaning Darvish presumably won’t be in attendance for Opening Day festivities at Petco Park. Instead, he'll likely throw in a camp game, before joining the Padres for the second game of their season (lining him up to pitch the sixth).

The race for the No. 6 spot
That leaves a vacancy in the rotation before Darvish, as the Padres plan to open the year with a six-man staff. Musgrove isn't an option, meaning San Diego has a decision on its hands.

“We’ll have to figure that one out,” Melvin said, coyly.

Based on spring performance, left-hander Jay Groome appears to be the leader for that role. Groome, who landed in San Diego in the deal that sent Eric Hosmer to Boston, posted a 1.29 ERA across five spring outings, impressing with his increased fastball velocity and smoother delivery.

“I’m feeling good, cleaned up my mechanics,” Groome said. “Took it into camp and really tried to show these guys what I could do and challenge some of these hitters. Had some good results.”

Also in the mix for that No. 6 role are Brent Honeywell Jr., Julio Teheran and Ryan Weathers. If Groome wins the job, the Padres still seem destined to carry one of those three in a long-relief role. It’s possible that one of their length righties -- say, Honeywell or Nabil Crismatt -- will follow Groome in a piggyback-type outing.

Musgrove's return
Musgrove had done everything in his power to avoid beginning the season on the IL. Melvin even called his quick recovery from a fractured toe “miraculous.”

But the state of the rotation and the desire to ensure that Musgrove is properly built up left the Padres with no other choice: Musgrove will begin the season on the IL. Otherwise, the team wouldn’t have been able to carry enough length in its bullpen, and it might have rushed Musgrove at a pace it wasn’t comfortable with.

That said, Musgrove isn’t expected to be absent for very long. San Diego can back-date his IL stint to March 27, three days before the start of the regular season. That could set him up to return April 11 in New York, at the tail end of the Padres’ second trip through the rotation.

It’s later than they’d have liked to have their trio of aces in action together. But it also might set up this appetizing prospect:

The Padres return to Citi Field for a rematch of their tense National League Wild Card Series against the Mets April 10-12. It could be an early litmus test for two contenders.

Given the current trajectories, there’s a distinct possibility that the Padres line up Darvish, Musgrove and Snell.