GLENDALE, Ariz. -- Chris Paddack has dialed back all the talk of his desire for an Opening Day start.

Evidently, his performance this spring is doing enough of the talking.

The Padres' right-hander worked three scoreless frames on Monday, allowing a pair of seeing-eye singles in their game against the White Sox at Camelback Ranch. He's now worked five innings this spring and has yet to allow a runner past second base.

Barring injury, it's hard to envision a scenario in which Paddack doesn't take the ball on March 26 against the Rockies at Petco Park. He's been sufficiently dominant this spring. Right-handers Dinelson Lamet and Garrett Richards had served as Paddack's primary competition. But Lamet didn¡¯t debut until Saturday, and Richards won't take the ball until Tuesday.

"Right now I'm trying to stick with what I do best, eliminate all the noise, just going out there and competing," said Paddack when asked about his case for the Opening Day nod. "If we all hold each other accountable in this rotation, if we all push each other with that friendly competitive nature that we have, good things are going to happen.

"We need five horses this year to get to October. If I get to lead the group, then I do. If I don't, like I've said before: We've got five aces."

As usual, Paddack relied mostly on his fastball/changeup mix Monday. But he added a few extra curveballs. Paddack has spent most of the spring trying to develop that third weapon.

"Stay aggressive, attack the hitters, but I also wanted to work the curveball," Paddack said. "That was probably the most I've thrown it in a long time."

Results were mixed. Paddack spiked a few curves early -- which he said was a product of his gripping the baseball too tightly. By the third inning, he was locating it better and his velocity had ticked back closer to 80 mph.

Padres slow-playing Castillo
Left-hander Jos¨¦ Castillo has been placed on a slow progression this spring after missing most of the 2019 season due to injuries to his forearm and middle finger. As a result, Castillo is unlikely to appear in game action until mid-March, leaving his status for Opening Day in question.

"A little bit from the finger and some of the injuries he's dealt with, we just felt with him -- maybe he's good to go now -- but we wanted to make sure that he's done everything and we've stuck by the book and not skipped one step," said manager Jayce Tingler. "He's thrown the ball extremely well. We just don't want to step on the gas and have a mini setback. We want to make sure everything is getting done. We don't want to rush him one bit. Right now, he has been on-plan."

Tingler wouldn't offer a target date for Castillo's spring debut. But he noted Castillo was at least a week behind the progressions of top pitching prospects MacKenzie Gore and Luis Pati?o.

As a reliever, Castillo doesn¡¯t need to be built up in quite the same way -- meaning there's still a chance he forces his way onto the Opening Day roster. He'll have to do so in a shortened time frame, but Tingler warned against ruling Castillo out.

"He's got the trump card," Tingler said. "Because he's 6-foot-4, has a sneaky fastball and a wipe-away slider."

Castillo posted a 3.29 ERA with 52 strikeouts in 38 1/3 innings in 2018. But he pitched only two-thirds of an inning last year, missing the first four months because of a flexor strain in his left forearm and the final month and a half with ligament damage in his middle finger.

Tingler on tight 2B race
The Padres second-base battle won't end when Spring Training does.

"We're going to get through the end of camp, and maybe guys can take a half-breath and say, 'I made the team,'" Tingler said. "But then the season starts. We can't let up. We've got to keep getting better. We've got to keep pushing. We want to compete each and every night. I don't think it ends at the end of camp."

Jurickson Profar, Brian Dozier and Greg Garcia headline a group of six or seven candidates who could see time at second base. Because of the Padres' solidity at the other three infield spots, they might have room to keep as many as three or four second-base options on the roster.

If that's the case, Tingler seems poised to rotate at second base -- either by riding the hot hand or playing matchups. Ty France, Jake Cronenworth, Owen Miller and Esteban Quiroz are also in the mix for a utility spot.

Up next
Richards is slated for his first start of the spring on Tuesday when the Padres host the Brewers at Peoria Stadium at 12:10 p.m. PT. Richards signed with San Diego last offseason, and he returned from Tommy John surgery to make four starts in September.

But make no mistake: The Padres acquired the hard-throwing right-hander to be a difference-maker this year. Lefty relievers Matt Strahm and Drew Pomeranz are also slated to pitch.