SAN DIEGO -- The Padres’ thin rotation was stretched even thinner on Wednesday morning.

Left-hander Matt Strahm -- off to a strong start in his first full season as a starting pitcher -- was placed on the 10-day injured list with soreness in his left side, in the area of his rib cage.

The Padres don't expect Strahm to miss much more than the minimum 10 days. The 27-year-old left-hander spent last season in the bullpen, where he threw just 61 1/3 innings. The team was always going to cautious with his progression this year.

"It's something he could potentially pitch through, but at this point, we decided to give him a little bit of rest," said Padres manager Andy Green. "This isn't unanticipated to see him miss a start every once in a while. We're probably going to pick those times when he's feeling something to take the opportunity to do that."

In 11 starts this season, Strahm owns a 4.03 ERA. He said the rib soreness has bothered him for a few starts, but he wouldn't use it as an excuse for his poor outing on Sunday. Strahm surrendered seven runs to the Marlins over 4 1/3 innings, and his ERA jumped by almost a full run.

Until that outing, Strahm had been one of San Diego's most effective starters, having transitioned seamlessly from the bullpen to the rotation.

"It's super frustrating, obviously," Strahm said. "You never want to do this. My plan was to go gate to gate. That was obviously what I'd worked for all offseason. It's a little bump in the road, but that's all it should be."

The Padres haven't filled in the blanks for who might replace Strahm in the rotation. They'll need to find someone by the weekend, as Strahm was scheduled to start Saturday against Washington.

It seems likely that San Diego bumps Eric Lauer's start from Sunday to Saturday. That could leave Sunday as something of a bullpen day, ahead of Monday's off-day. Robbie Erlin has already started one of those this season.

Left-hander Logan Allen, the team's No. 6 prospect, seemed like an option to start in Strahm’s place. But Allen started Wednesday afternoon for El Paso instead.

In any case, the Padres plan to monitor the workloads of both Strahm and right-hander Chris Paddack this season. Both were limited in 2018 after returning from major surgeries. As a result, the two will get extra rest for almost every minor ailment they encounter this season.

"We came into the year understanding there'd be limitations on them," Green said. "It just makes sense to pay attention to their bodies along the way and try to do what's best for them."

Injury updates

• In two rehab games this week, Fernando Tatis Jr. is 2-for-5 with three walks and a stolen base. The rookie shortstop was not in the lineup for Double-A Amarillo on Wednesday afternoon.

Green said the off-day was planned, but he added that the organization would huddle to determine the next course of action for the 20-year-old phenom. Tatis has been out since April 28 with a left hamstring strain.

"We'll circle up today and talk a little bit about where he is," Green said.

• Left-hander Jose Castillo is expected to begin a rehab assignment in the coming days as he fights his way back from a flexor strain in his left forearm. Castillo’s absence has been felt in the Padres' bullpen. As a rookie, he posted a 3.29 ERA with 52 strikeouts over 38 1/3 innings last season.

• The Padres promoted Wednesday's starter Cal Quantrill to take Strahm's place on the roster. They also activated right-hander Miguel Diaz from the 60-day IL following his arthroscopic right knee surgery in February. Lefty Brad Wieck, who has struggled over the past week, was optioned to Triple-A El Paso

• To clear room on the 40-man roster, the Padres designated outfielder Alex Dickerson for assignment. Dickerson's tenure with San Diego has been marred by injury, and he missed the past two seasons because of back and elbow surgeries. In a crowded outfield mix, Dickerson was merely a roster casualty on Wednesday morning, after batting .158 in 12 games this season.

"We've always appreciated what Alex brings," Green said. "We really think it's a professional at-bat. ... We have a large number of outfielders that we like a lot, and Franchy Cordero, at some point is going to be coming back. Sometimes you've just got to make tough decisions."

• Right-hander Dinelson Lamet, working his way back from April 2018 Tommy John surgery, made his second rehab start for Class A Advanced Lake Elsinore on Tuesday night. He struggled with his command, allowing five runs on five hits and three walks over 2 1/3. Lamet struck out four.