SAN DIEGO -- For one day -- and one day only -- the Padres had the dominant left-handed reliever they'd been waiting for all year.

Then, as quickly as Jose Castillo's season started, it was over.

Castillo will miss the remainder of the 2019 campaign with a torn ligament in his throwing hand, manager Andy Green said Saturday. Surgery isn't required, and the club expects Castillo to make a full recovery -- potentially as soon as October. (Castillo even informed Green that he intended to return for the postseason.)

"We're incredibly disappointed for him," Green said. "He'd worked really hard to get back. To have a two-out outing be his only outing of the regular season is tough -- tough for him, tough for us. We're hoping his recovery is good and that he's a productive pitcher for us for a long time. We really expect him to be."

With Matt Strahm in the season-opening rotation and Brad Hand traded to the Indians, the Padres had been counting on the 23-year-old Castillo to take over as their primary lefty relief option this year. In his 2018 rookie season, Castillo posted a 3.29 ERA over 37 appearances with 12.2 strikeouts per nine innings.

But Castillo sustained a flexor strain in his left elbow that kept him out for five months. He was nearing a mid-June return when he began experiencing further tightness in his elbow. That setback prolonged his rehab by another month and a half.

At long last, Castillo returned to the Padres' bullpen on Thursday night, walking a batter and hitting a batter before striking out two Rockies. After he whiffed Daniel Murphy, he began shaking his hand in discomfort.

Castillo was placed on the injured list Friday, and he underwent an MRI which Green said revealed that the "pulley system" attaching Castillo's middle finger to his bone had been torn.

Green wouldn't discuss whether Castillo might play winter ball. Unlike with a starter, it isn't at all imperative that he build his innings. The Padres' primary concern will be getting Castillo healthy for the 2020 season. They still feel as though he can be an impactful piece of their bullpen. They'll just need to wait longer than they'd hoped.

Starters get a test
Beginning Sunday, Dinelson Lamet, Joey Lucchesi, Eric Lauer and Cal Quantrill will all pitch on four days of rest in their next turn through the rotation. For 29 other teams, that probably doesn't qualify as news. But it's the first time this year the Padres will start four straight pitchers on what's considered "normal" rest in the big leagues.

The Padres have been cautious with their young starters this season -- including Chris Paddack, who's been placed on a strict innings limit. They've gone basically the entire year using an every-six-days plan for their rotation.

So, what's changed? Well, Strahm, who was on a Paddack-like innings limit, has shifted to the bullpen. Lauer and Lucchesi are already equipped to pitch every fifth day, having done so last year. Lamet and Quantrill won't be approaching any sort of limits either -- Lamet because he missed the first half of the season and Quantrill because he spent time in the 'pen.

"These are things we're comfortable doing with this group of guys, understanding what their workload is for the rest of the season," Green said.

Injury updates
• Outfielder Franchy Cordero rejoined the Padres on Thursday when they returned for the homestand. He's been taking batting practice with the club, running the bases and getting light outfield work.

Cordero has been out since early April -- first with a left elbow sprain, then with a left quad injury that he sustained while on a rehab stint. The Padres remain hopeful for a September return for the lefty slugger.

• Right-hander Jacob Nix has also rejoined the club, and he threw a bullpen session at Petco Park on Saturday. Nix is working his way back from a right UCL sprain he sustained during Spring Training, and he's slated to make his fourth rehab start next week -- presumably Tuesday for Class A Advanced Lake Elsinore.