HOUSTON -- The good news for the Astros is they’re 3-1 after taking three of four games from the Mariners to begin the season at Minute Maid Park, setting up a much-anticipated showdown with the Dodgers on Tuesday and Wednesday. The bad news? Their pitching staff is in tatters.

The Astros rallied from an early three-run deficit to beat the Mariners on Monday night, getting a three-run homer from Alex Bregman in the third to take the lead and adding on with a Jose Altuve homer in the fifth. Rookie Brandon Bielak bailed out their beleaguered bullpen with 3 1/3 innings of relief, allowing one earned run, to get the win in his big league debut.

• Box score

• Bregman's 100th homer is way gone

The first series of the season, though, has provided more concerns than answers for an Astros team that has scored 29 runs but has seen numerous pitchers go down with injuries and a bullpen that’s now full of unproven arms.

“I like our defense, big time,” manager Dusty Baker said. “We can catch the ball and we can certainly hit it. We’ve got guys that aren’t even hitting yet.”

Here’s three things we learned about the defending American League champions with one series under their belt:

The offense remains potent
The Astros, who set a Major League record last year with a .495 slugging percentage and posted a franchise-record .848 OPS, have a lineup that remains among the deepest in the league. The Astros are averaging 7.3 runs per game and are slashing .280/.375/.500, and that’s with George Springer (1-for-16) struggling at the top of the lineup and Bregman and Altuve just getting started.

Houston has hit only five homers in four games, so it stands to reason there’s plenty of thunder yet to come. Still, they’re getting timely hits (15-for-45 with runners in scoring position) and enjoying production at the bottom of the order, where catchers Martín Maldonado and Dustin Garneau have combined to go 6-for-14.

“Very rarely do you start the season with everybody hot at the same time, especially when you’ve got an abbreviated Spring Training,” Baker said.

Ultimately, it’s going to be up to Springer, Altuve, Bregman, Michael Brantley, Yuli Gurriel and Carlos Correa to carry the offense, but the Mariners had no answers for the Astros’ bats.

Injured arms are piling up
The Astros began the season with veteran right-handers Austin Pruitt and Brad Peacock on the injured list, and Jose Urquidy -- expected to be in the rotation to start the year -- on the injured list for undisclosed reasons. The pitching staff suffered a major blow when it was revealed Sunday ace Justin Verlander has a forearm strain and would be shut down for two weeks, punching a huge hole in the rotation.

Then, after Monday’s win, Baker revealed All-Star setup man Ryan Pressly, who hasn’t pitched in the first four games, is dealing with elbow soreness suffered Sunday. And he said right-hander Chris Devenski, who gave up three runs in the eighth inning in Sunday’s 7-6 loss, also has elbow soreness.

Baker said the short ramp-up to the start of the season is taking its toll on pitchers.

“It’s all around baseball; it’s everywhere,” he said. “I’m hoping we learned a lesson by this. It couldn’t be helped because of the coronavirus, but I’m just hoping we don’t see any more injuries around the league, especially on our team.”

Astros closer Roberto Osuna, who got the save Monday, and the inconsistent Joe Biagini are the only healthy relievers who have more than a year of service time on the roster. As a result, Houston is carrying eight rookies in its bullpen and may have trouble filling innings. The Astros need more pitching.

Which leads us to…

The kids are all right
No one would have dreamed in March that Brandon Bailey, Cristian Javier, Bielak, Blake Taylor and Enoli Paredes would all make their Major League debuts by the end of July. It took a coronavirus shutdown to expand rosters and a bevy of injuries for the Astros to have five rookie pitchers get their feet wet in the big leagues in the first four games. And another, Nivaldo Rodriguez, was called up Monday and has yet to pitch.

Bielak had a strong debut Monday by throwing 3 1/3 innings, and the only lefty in the group, Taylor, has looked solid so far. Javier and Paredes have great stuff and could have promising futures, too. The Astros would rather have them pitching in the Minor Leagues and developing, but desperate times call for desperate measures.

“It was a great debut for him,” Baker said of Bielak. “He saved our tail. He came in today and threw a lot of strikes, competed, attacked, executed.”

The Astros will need the youngsters to keep rising to the challenge, but they need their veteran arms to get healthy even more. And in a hurry.