Aaron Bummer reportedly signs minor league deal with Cubs after Atlanta release

Aaron Bummer, the left-handed reliever released by Atlanta last week, has reportedly agreed to a minor league deal with the Cubs, per Bob Nightengale of USA Today. Per the report, Bummer is expected to report to Triple-A Iowa at some point in the coming days. The deal does not place him on Chicago's 40-man roster — that question, like most of the interesting ones here, remains open.

What happened

Per Nightengale's report, Bummer and the Cubs reached agreement on a minor league contract after Atlanta cut him loose following a difficult stretch to open the 2026 season. He had posted a 7.63 ERA over 15 1/3 innings with the Braves before the organization moved on. His final outing with Atlanta was a particularly stark one: six runs allowed on three hits and five walks in a single inning against Miami.

A minor league deal, as a general matter of roster mechanics, does not add a player to a club's 40-man roster. Bummer would need to be added to that list before any potential call-up to the active roster, which sits at 26 players through the end of August. Chicago is, for now, taking a look at a reclamation project from a position of minimal roster commitment — the baseball equivalent of kicking the tires with the engine still running.

Why it matters

The appeal here is not hard to locate, even if the 2026 numbers make it easy to forget. Bummer was a legitimate left-handed bullpen weapon for Atlanta across the two prior seasons, posting a sub-4.00 ERA in both years while generating plus ground-ball rates. Two seasons ago he carried a 28% strikeout rate, a figure that would make any pitching coach nod approvingly. That number slipped to 21.7% last season — a pedestrian mark, and, per MLB Trade Rumors, an alarming precursor to what has unfolded in 2026.

Left-handed relievers with a track record of generating ground balls do not grow on trees, and the Cubs are presumably betting that the version of Bummer who was useful in Atlanta is still somewhere in the building, even if the 2026 line suggests he has temporarily misplaced the address. A minor league deal is a low-cost way to find out.

The numbers

The 2026 figures are not subtle. Bummer's 7.63 ERA over 15 1/3 innings is the headline, but the underlying rates are what make the number feel less like bad luck and more like a structural problem. His 16.9% strikeout rate and 13% walk rate were both described by MLB Trade Rumors as awful — and the combination of those two figures in a reliever is the kind of thing that tends to produce a 7.63 ERA rather than merely accompany one.

The six home runs allowed in 15 1/3 innings is the detail that raises the most eyebrows. His 46.2% ground-ball rate was described as decent, which makes the home run total feel somewhat incongruous — ground-ball pitchers are not supposed to be surrendering home runs at that clip. Whether that reflects something mechanical, something about pitch quality, or simply a brutal stretch of variance is not something the report addresses, and it is not something the desk will speculate about.

The prior version of Bummer — sub-4.00 ERA, plus ground-ball rates, a strikeout rate that peaked at 28% — is the pitcher the Cubs are presumably hoping to recover. The gap between that pitcher and the one who surrendered six runs in one inning against Miami is the entire story of this signing.

What we don't know yet

Is Bummer heading straight to Iowa?

Per the report, he is expected to report to Triple-A Iowa at some point in the coming days. Beyond that, the report does not specify whether the minor league deal includes an opt-out clause or a major league invitation trigger, both of which are common features of such contracts but are not reported here. No specific timeline for any evaluation or roster decision is mentioned.

The cause of Bummer's 2026 struggles is not addressed in the report — no mechanical explanation, no injury history cited, no diagnosis offered. What the report establishes is that Atlanta released him after a rough stretch, and the Cubs have decided the minor league price of admission is worth paying to find out whether the problem is fixable.

It is also worth noting that Bummer's strikeout rate had already been trending in the wrong direction before this season. The drop from 28% to 21.7% between his two Atlanta seasons was flagged by MLB Trade Rumors as a precursor to the current difficulties. Whether Iowa provides the environment to address whatever is driving that trend is genuinely unknown.

What to watch

The obvious follow-up question is whether Bummer can stabilize his strikeout and walk rates at Triple-A Iowa before any potential 40-man addition becomes a conversation. A 13% walk rate in the majors is the kind of number that tends to get a reliever released; the same rate in Triple-A would not inspire confidence either.

If Bummer does find something resembling his prior form — ground balls, fewer free passes, the strikeout rate climbing back toward useful — the Cubs would face a straightforward roster decision about whether to add him to the 40-man and bring him to the active roster. That decision is entirely speculative at this point, and the report does not suggest any timeline for it.

For now, the story is a left-hander with a complicated recent history and a clear prior track record of usefulness heading to Iowa on a minor league deal. The Cubs have made a low-commitment bet that an earlier, more effective version of Aaron Bummer is recoverable. Triple-A will begin to answer that question before the major league roster ever has to.