MIAMI -- After putting together their best 28-game start to a season since 2012, the Indians were dealt a blow when the calendar turned to May.

Ace Corey Kluber exited Wednesday night's 4-2 loss to the Marlins in the fifth inning after being struck by a comebacker. After the game, it was revealed that he sustained a non-displaced fracture of the right ulna, the longer of the two bones in the forearm. He will be re-evaluated in Cleveland on Thursday to confirm the diagnosis and determine a timetable.

"I worry about the players," Indians manager Terry Francona said. "You always figure that we’ll figure something out as a team. But you worry about the guys because you care about them. But you saw it. It looked ugly. You just worry about guys."

According to Statcast, Brian Anderson connected on a first-pitch, 90.6 mph four-seam fastball from Kluber and sent it back up the middle with an exit velocity of 102.2 mph. Kluber tried to protect himself from the liner, which struck his forearm, before attempting to glove flip the ball to first in obvious pain.

Francona, head athletic trainer James Quinlan and the infielders gathered near the Marlins Park mound to visit Kluber, who did not attempt a warmup throw before departing.

The usually stoic Kluber, who was being fitted for a cast and didn't speak to media following the game, could be seen heavily exhaling.

"I've never seen him show any emotions on the mound, but today, he got hit by a line drive," catcher Roberto Perez said. "As a pitcher, I'm sure right away your head starts spinning. 'Is it broken?' Tito kept asking him, 'What do you feel?' He was just numb. At that point, you start thinking the worst. We can't control those things. That's just part of baseball. It's tough to see him go, especially [since] he's a big part of our team."

Kluber had given up three runs on eight hits with three strikeouts, no walks and one hit batter over 4 2/3 innings. Of his 57 pitches, 43 went for strikes in his first career appearance against the Marlins.

Right-hander Dan Otero came on in relief and recorded the final out of the fifth with the Tribe trailing, 3-1.

"It's tough. It's never what you want to see," Anderson said. "I don't even know what to say. It's sad to hear. It's baseball.

"You're just hoping that nothing bad has happened. We're out there competing against each other, but nobody on our team wants anybody on their team to get hurt. I know it's the same way the other way around.

"I just hope that he has a good recovery and comes back the Kluber that everyone knows that he is."

Despite a rough start to the season (2-3, 5.80 ERA), losing the two-time AL Cy Young Award winner is a tough hand to be dealt to Cleveland's rotation, which is already without Danny Salazar (right shoulder rehab) and Mike Clevinger (upper back strain), both of whom are on the 60-day injured list.

While we don’t have a firm timetable, we can look back at players who sustained a similar injury to get a sense of when we might be able to see Kluber on the mound again. Blue Jays prospect Nate Pearson sustained a non-displaced fracture of his ulna when he was struck by a line drive in his first Minor League start on May 7 of last year. Pearson was in a cast for five weeks and back throwing live batting practice in August, although he didn’t pitch in another game that season. Though not a pitcher, Hunter Pence had a non-displaced fracture of his left ulna on March 5, 2015, and played his first regular-season game that year on May 16.

"I know he's working to get back..." Perez said. "He's going to be Kluber. There's no panic, just got to keep playing baseball."

So who's the next man up?

Since Clevinger's injury, the Indians have been able to run out a four-man rotation thanks to off-days. They also utilized Jefry Rodriguez, who was set to be recalled on Tuesday, for spot starts. Now the club will need someone to fill in the fifth spot.

Below are some options the Tribe could turn to:

1. Asher Wojciechowski

40-man roster? No

The 30-year-old right-hander is 2-0 with an 0.82 ERA and 0.96 WHIP through four starts with Triple-A Columbus. Wojciechowski last pitched in the Majors in 2017 as a member of the Reds. He has 30 career MLB outings (11 starts), with a 6.64 ERA over 78 2/3 innings.

2. Cody Anderson

40-man roster? Yes

Anderson has made one appearance since being optioned to Columbus last week. Though the 28-year-old right-hander pitched three scoreless innings on Sunday, he only threw 36 pitches. Anderson would likely need to be stretched out -- or perhaps serve as an opener of sorts.

3. Chih-Wei Hu

40-man roster? Yes

In his first season in the Indians' organization, the 25-year-old right-hander is 0-1 with a 5.01 ERA and 1.41 WHIP through five starts. On Sunday for Columbus, he put together his best outing: two runs over 6 2/3 innings with six strikeouts and one walk.

4. Michael Peoples

40-man roster? No

The 27-year-old right-hander has yet to make his Major League debut, but he has gotten off to a strong start in Columbus. Peoples is 3-0 with a 2.96 ERA and 1.28 WHIP over five games (four starts) spanning 27 1/3 innings.

5. Adam Plutko

40-man roster? Yes

Plutko, on the seven-day injured list in the Minors with a forearm strain, began a throwing program last week. The 27-year-old right-hander has yet to pitch in a game, so his timetable doesn't make him the likely next man up.

"I think we've got some guys that have big shoes to fill in," Perez said. "Whoever comes up, try not to do too much and get the job done. I don't know who's coming up, taking his spot, but I'm sure they will get the job done."