The Arizona Diamondbacks struggled offensively during the 2026 season, despite a reputation of excellence.

They had difficulty producing with runners in scoring position. They had the worst first base situation in baseball by OPS (.636 and dead last in MLB).

And yet, the most concerning aspect of the Diamondbacks' roster is not first base, nor DH, nor anything offense-focused. It's not even bullpen-related. It's the starting rotation that is in one of the most precarious spots of the entire roster.

Diamondbacks' starting rotation severely lacking for depth

Enough cannot be said about the job done by veteran left-hander Eduardo Rodriguez and young righty Brandon Pfaadt last season.

Rodriguez led Arizona's rotation with a 2.89 ERA, while the Diamondbacks went 23-9 in games he started. Pfaadt rebounded from a brutal start to the year, coming back from Triple-A Reno to massive success and a 3.38 ERA as a starting pitcher.

Michael Soroka was a positive, as well. He produced a 3.41 ERA over 116 innings, but battled injury and has since declined his mutual option for 2027. He'll be a free agent.

But as it stands, the Diamondbacks' rotation is not in great shape heading into 2027. With Soroka a free agent, Arizona's starting five consists of Rodriguez, Pfaadt, Merrill Kelly, Corbin Burnes and Ryne Nelson.

Kelly had a poor 2026, struggling with command to the tune of a 4.94 ERA. Nelson held a 4.97 ERA when he went down with a significant elbow injury, only barely returning in limited fashion as a reliever towards season's end.

Burnes (7.84 ERA) was nothing resembling his former self, making three ineffective starts once finally returned from the Injured List. As a whole, the D-backs ranked 19th in baseball with a 4.28 team ERA.

But the Diamondbacks had to dip heavily into their minor league depth. They got semi-significant innings from rookies like Kohl Drake (6.53 ERA), Mitch Bratt (4.71 ERA) and Jose Cabrera 5.72 ERA.

No major league team can make its way through a 162-game season without testing its rotation depth. No number of quality starting pitchers is too many. The problem is, Arizona may not even have five.

Rodriguez carries a chance of regression, especially considering his peripherals such as FIP (3.89) and xERA (4.27) were much higher than his raw ERA.

Meanwhile, Pfaadt has yet to string together two high-quality seasons. Burnes may not return to ace form after multiple significant injuries. Kelly may not be able to regain his command in his age-38 season. Nelson is an uncertainty, as well.

So unless Drake, Bratt, Cabrera or another prospect takes a massive leap at the MLB level, the Diamondbacks are one injury or one severe regression season away from having one of the least effective rotations in baseball.

In short — this is an area they have to address this offseason, whether in free agency or via trade. Bringing Soroka back could help solve that, but with expectations of a reduced payroll, that might not be viable.

But the Diamondbacks simply can't go into 2027 with only the arms available to them now. There just isn't enough reliable depth.