SAN DIEGO -- The Padres insist the early test their rotation is facing isn't any bigger or more daunting than what they'd prepared for. They knew all along that the 2021 season would present a unique set of challenges -- and sure enough, the final two places in their starting five have already become a revolving door. Three pitchers have exited starts early this season because of injury. Another, right-hander Chris Paddack, is on the IL for undisclosed reasons.

As such, the Padres needed to find a starter from somewhere within their system for Monday night. One option, of course, was MacKenzie Gore -- the best pitching prospect in baseball, as ranked by MLB Pipeline. Gore is 22 years old and appears in line for a big league breakthrough at some point this season.

So why not now? Why not Monday night against the Pirates? The Padres needed a starting pitcher, and the landing spot seemed soft enough.

They opted to start Miguel Diaz instead.

So what gives? The Padres are one of the Majors' most aggressive organizations when it comes to promoting top prospects -- as evidenced by their handling of Fernando Tatis Jr. and, more recently, Ryan Weathers, another tantalizing young left-hander.

When manager Jayce Tingler announced Diaz as his starter following Sunday's game against the Giants, he was asked about Gore and the nature of a potential callup.

"The main thing is: We'll call him up when the organization feels like we're on a roll and ready to go," Tingler said. "My guess is we're going to need him at some point this year, as we're going to need other guys. But we're not going to force anything. We're not going to rush anything. We've got guys we believe can get the job done. We're going to do what's right for our young players."

The truth is, of course, that Gore hasn't forced the Padres' hand the way Weathers and Tatis did. He struggled during Spring Training, especially with his control. Gore's stuff remains as electric as it's ever been. But he's not throwing his lively fastball for strikes as consistently as he needs to be.

According to sources, that trend has continued into games at the team's alternate training site. At the same time, Gore continues to show the same upside that makes him one of the best prospects in baseball.

Perhaps some of his struggles can be attributed to the bizarre nature of the past 20 months. The Triple-A El Paso season is slated to begin on Thursday, marking the first time Gore is scheduled for regular starts since August 2019. Gore finished that season with a 1.69 ERA and was named MLB Pipeline's Minor League Pitcher of the Year. Aside from a few Spring Training and alternate-site outings, he hasn't pitched with any regularity since.

In an ideal world, Gore will get a handful of starts at El Paso, where he'll find a groove and regain the elite command that helped elevate him into one of the sport's top prospects in the first place. If he establishes that, a callup would presumably follow. Chances are the Padres will need him -- particularly as they monitor the workloads of Weathers and Dinelson Lamet this season.

But until then, the Padres would like to avoid an early callup -- unless injuries force their hand out of necessity. With Lamet (right forearm tightness) and Weathers (left arm fatigue) still questionable and Paddack on the IL, it’s probably getting close to that point. But as evidenced by Monday's decision, the Padres aren’t quite there yet.

Worth noting

• The Padres optioned righty reliever Aaron Northcraft to their alternate site, recalling fellow right-hander Nabil Crismatt in his place. Crismatt, a multi-inning option out of the 'pen, has allowed three earned runs over 8 2/3 innings this season.

• First baseman Eric Hosmer was out of the starting lineup Monday night. Tingler noted that Hosmer's absence was merely a scheduled off-day, timed nicely to coincide with a left-handed starter on the mound for Pittsburgh.

• Austin Nola received his second start behind the plate since his return from the injured list last Wednesday. Ultimately, the Padres expect Nola to slide into a regular starting role, but for now, the Padres will build his workload slowly. Nola, who missed four weeks with a fractured finger, will share time evenly with Victor Caratini, Tingler said.