Giants prospect's breakout season ends under the knife

Trevor McDonald spent the first half of 2026 doing exactly what the Giants needed: eating innings as a rookie in a rotation that badly needed stability. Then his elbow started barking, and now his year is done.

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Trevor McDonald To Undergo Tommy John Surgery t.co/SPAYYbJgdC

The trouble started on July 21 against the Royals at Kauffman Stadium, when McDonald walked off the mound with a trainer before the bottom of the fifth. He'd already worked 4 innings, allowing 3 runs on 4 hits with 3 strikeouts and 2 walks, and the Giants put him on the 15-day IL with what was initially called an elbow strain.

That diagnosis got worse fast. Doctors found a moderate UCL sprain, McDonald sought a second opinion, and by this week the answer was the one every pitcher dreads: full Tommy John. The 25-year-old righty had been a rotation fixture since May in his first extended taste of the majors, running a 5.12 ERA over 70 1/3 innings with a strong 55.2% ground-ball rate but a modest 18.4% strikeout rate.

Recovery from Tommy John typically runs 14 to 16 months, which wipes out the rest of this season and realistically all of 2027. Best case, McDonald is back throwing in games by spring training 2028. The Giants still control him for 6 more seasons, so it's not a financial gut-punch, just a lost year and a half of development for a guy who was finally getting a real look.

The timing stings on the roster-building side too. San Francisco is already staring down a thin pitching picture with names like Robbie Ray and Tyler Mahle possibly moving before the trade deadline, and now a homegrown rotation piece is off the board for a year and a half. For fantasy managers who scooped McDonald up as a streaming option, it's an easy drop — and for the Giants, it's another arm to replace on the fly.