Blake Walston reinstated by Diamondbacks from 60-day IL as rosters expand to 28

What happened

The Arizona Diamondbacks announced the reinstatement of left-hander Blake Walston from the 60-day injured list, effective as active rosters expanded from 26 to 28 players on September 1. The club also reinstated outfielder Lourdes Gurriel Jr. from the 10-day injured list on the same day, accounting for both additions the expansion allows. To create a 40-man spot for Walston, right-hander Ryan Thompson was transferred to the 60-day IL, per the club's announcement.

Walston, 25, is expected to slot into the bullpen rather than the rotation — at least for now.

Why it matters

The road back for Walston has been a long one, and the calendar has not been kind. He made his major league debut with Arizona in 2024, appearing in seven games and allowing nine earned runs across 18 1/3 innings. That was the entirety of his big-league résumé before Tommy John surgery in March of 2025 took the rest of that year and the majority of this one away from him.

He has been on a rehab assignment for almost a month, per MLB Trade Rumors, but his outings have been limited to one to two innings at a stretch. That workload pattern is what shapes his immediate role: the Diamondbacks are bringing him back as a reliever, not a starter, even though he worked as a starter throughout his minor league career. MLB Trade Rumors noted that the club may look into stretching him out again in the future, but for now the bullpen is where he lands.

The timing is worth noting. September roster expansion is the one moment in the baseball calendar when a team can absorb a pitcher who is not yet stretched out, because the expanded active roster creates room to carry arms who might only be available for an inning or two. For a left-hander returning from Tommy John surgery, that context is genuinely useful — it is a softer re-entry point than, say, a pennant race in July when every roster spot carries maximum weight.

The 60-day IL also carries a specific mechanical function: it removes a player from the 40-man roster count, which is why Thompson's transfer was necessary to clear space. That is routine roster architecture, but it is worth understanding — Walston's return required moving another piece on the board.

Where the club stands

### Is Arizona still in the Wild Card race?

Yes — and barely, which is precisely what makes the next few weeks matter. The Diamondbacks enter September at 74-68 (.521), sitting third in the NL West, 10.5 games behind the division leader. The more pressing figure is the Wild Card standing: Arizona ranks fourth in the NL Wild Card race, sitting 0.5 games relative to the cut line. That is a margin thin enough to feel with your fingertips. The club arrives at this moment on a one-game losing streak.

The schedule ahead does not offer much in the way of breathing room. On Tuesday, September 1, Arizona hosts the Philadelphia Phillies at Chase Field, with Eduardo Rodriguez projected to start against Jesús Luzardo. The series continues Wednesday, September 2, with Taylor Clarke lined up against Andrew Painter. The club then travels to Houston for a Friday, September 4 start at Daikin Park, where Merrill Kelly is projected to face Cristian Javier.

That is a stretch featuring the Phillies — a club with their own playoff ambitions — followed by a trip to Houston. The Diamondbacks' bullpen depth, and by extension Walston's availability, becomes a real operational question against that kind of competition.

What we don't know yet

The club's announcement does not specify how Walston will be used beyond the general expectation that he joins the bullpen. His rehab outings have been capped at one to two innings, per MLB Trade Rumors, but whether Arizona intends to keep him in that range or begin extending him is not yet clear. MLB Trade Rumors noted the possibility of stretching him out again in the future without attaching a timeline or a firm decision to it.

Thompson's transfer to the 60-day IL is reported as a roster-mechanics move to open the 40-man spot, but the nature of his situation beyond that is not detailed in the announcement.

Gurriel's reinstatement from the 10-day IL was announced alongside Walston's, but the announcement does not include details about his availability or any limitations coming off the injured list.

What to watch

The immediate question is how quickly Walston gets into a game and what his workload looks like when he does. A left-handed reliever returning from Tommy John surgery, working in one-to-two-inning bursts, is a specific kind of asset — useful in the right matchup, but not yet the multi-inning option he might eventually become if the club decides to stretch him out.

With Arizona sitting 0.5 games relative to the Wild Card cut line and a schedule that runs through Philadelphia and Houston in the first week of September, the margin for error in the bullpen is essentially zero. Walston's role in that mix — how often he pitches, against whom, and for how long — will tell you something about how the Diamondbacks view where he actually is in his recovery, as opposed to where the roster paperwork says he is.

The longer arc is whether this September stint functions as a genuine audition for a rotation spot down the road, or whether the bullpen role becomes more permanent. MLB Trade Rumors flagged the possibility of stretching him out again, but that is a future conversation. Right now, the Diamondbacks have a left-hander back on the active roster for the first time in the better part of two years, and a Wild Card race that has no patience for hypotheticals.