We wrote before the season that rotation depth would be the Cubs' greatest weapon in 2026 β that Jed Hoyer built a nine-deep pitching staff specifically because of how the 2025 postseason ended, when a cracked rib kept Cade Horton off the mound in the NLDS against Milwaukee. The theory was that no matter what happened, the Cubs would have enough arms to absorb a blow.
Seven games into the season, that theory is being tested. Horton exited Friday's start in Cleveland after just 17 pitches with right forearm discomfort and will be placed on the 15-day injured list. He's heading back to Chicago for imaging this weekend, with MRI results expected by Monday. Until then, everything is speculation β but the Cubs have decisions to make right now.
What Happened
Horton retired the Guardians in order in the first inning, throwing 95-96 mph. Everything looked normal. Then he walked Kyle Manzardo to lead off the second, threw a curveball and a 93.8-mph fastball to Bo Naylor β roughly 2 mph below his season average β and immediately looked toward the Cubs' dugout. Craig Counsell and trainer Nick Frangella came to the mound. Horton walked off. Marquee's Taylor McGregor reported he had tears in his eyes heading to the clubhouse.
Horton said afterward that the discomfort started as tightness in his wrist and migrated to his forearm during the outing. He made the call to stop rather than push through it β a decision that speaks to the maturity he's developed after a lat strain derailed his 2024 minor league season and the rib fracture ended his 2025 campaign. "I just wanted to be smart about it," Horton said. "I've been in this spot before and I've taken the other route where I keep going, and it ends up being worse."
Why It's Concerning β And Why There's Still Hope
The obvious fear: forearm discomfort is a common precursor to UCL problems, and Horton already had Tommy John surgery as a freshman at Oklahoma in 2021. Any time a pitcher who's had TJ feels something in the forearm, the alarm bells go off. The sudden velocity drop β 95-96 to 93.8 in one inning β adds to the concern. Counsell was measured but honest: "You take a pitcher out of a game in the second inning, you're concerned. He'll probably get imaging, and that's concerning, as well."
The reason for cautious optimism: Horton described the issue as wrist tightness that spread to the forearm, which isn't a textbook UCL symptom. He pulled himself immediately rather than pitching through it, which gives the injury the best chance of being something minor rather than something structural. He said he's "pretty hopeful." We won't know anything for certain until the MRI comes back. Until then, the Cubs have to plan as if Horton is out β and they have options.
Who Fills the Spot?
The Cubs didn't wait long to answer that question. On Saturday, the team called up left-hander Riley Martin from Triple-A Iowa to take Horton's roster spot. Martin's path to the big leagues is one of the better stories in the Cubs' system β he pitched at Division II Quincy University in west-central Illinois, threw in the mid-80s as a junior, had his senior season wiped out by COVID, nearly left baseball for pharmacy school, then came back for a fifth year and struck out 152 batters in under 79 innings. The Cubs took him in the sixth round of the 2021 draft, and his fastball now sits in the mid-90s and touches 98, setting up a slurvy breaking ball he throws as hard as his college fastball used to be.
Martin has worked almost exclusively as a reliever since 2022, so the expectation is that he'll slot into a long-relief role in the bullpen while Colin Rea slides into the rotation as Horton's direct replacement. That's the safe, obvious move β Rea did exactly this job all of last year when Justin Steele went down, made 27 starts, threw 159.1 innings with a 3.95 ERA, and came in for Horton on Friday to throw 3.1 solid innings (4 H, 1 ER, 4 K). He knows how to start, he knows how to fill in on short notice, and he's done it before.
Ben Brown remains the higher-upside option if the Cubs need another starter down the line. He's been sharp out of the bullpen this year, punching out nearly a third of the batters he's faced, and a new sinker he added this offseason has changed his pitch mix in a way that could make him more viable as a starter than his 5.92 ERA in that role last year would suggest. Javier Assad is also on the 40-man roster at Triple-A Iowa β his first start this week was rough (4 IP, 7 ER), but the track record across parts of four MLB seasons (3.43 career ERA) is longer than one bad outing. If this turns into a longer absence, the Cubs have options beyond the initial move.
The longer-term outlook has reinforcements coming, too. Justin Steele is tracking toward a return from his UCL surgery sometime in May or June, and when he's healthy, he's a legitimate frontline starter who changes the complexion of the entire staff. Further down the pipeline, top pitching prospect Jaxon Wiggins is developing at Triple-A Iowa β he's not ready for the big leagues yet, and the Cubs aren't going to rush him, but his presence in the system is another layer of depth if the injury list keeps growing.
The Bigger Picture
Horton joins a growing list of injured Cubs arms β Justin Steele (UCL surgery, likely not back until May or June), Jordan Wicks (forearm), Porter Hodge (elbow), and Shelby Miller (UCL, out for 2026). That's five pitchers on the IL before the second week of the season is over. The depth chart that looked so deep after the Angels series β Cabrera dazzling, Boyd bouncing back, Taillon solid β now has a hole at the top where the ace is supposed to be.
But this is exactly the scenario the Cubs built for. Cabrera and Boyd have both proven they can pitch at a high level. Taillon is functional. Imanaga gets his shot tonight. Rea steps into the rotation, Martin gives the bullpen another arm, and Brown, Assad, and others are waiting if the situation changes. The rotation won't be as good without Horton β nobody on this staff has his ability to work around hitters and generate swing-and-miss β but it can still be good enough.
The MRI will determine whether this is a 15-day absence or something much worse. The Cubs will hold their breath through the weekend and hope for the best on Monday.