The Arizona Diamondbacks arrive in Boston on Monday to open a three-game series with the Red Sox, and the opener has already been set up as a contrast in urgency. Mitch Bratt, a rookie southpaw, is listed to start for Arizona against a TBD Red Sox pitcher.
That is the kind of matchup that draws attention now because the Red Sox have lost three straight series and went 2-5 on their road trip, while Arizona is trying to keep pace in a tight postseason race. The Diamondbacks are out of a Wild Card spot and sit a game behind the Padres and Phillies, so every game in this set carries a little more weight than a normal August series.
Bratt is the name to watch on Monday. He has made seven starts in his rookie year and has thrown 33.2 innings, allowing 28 hits, five homers, 19 walks and 14 runs while striking out 25. The line gives him a 3.74 ERA, but his 5.31 FIP points to the part of the profile that still needs work. For a club trying to stay in the chase, that kind of start matters because it can either steady the rotation or force the bullpen into an early-night assignment.
Boston’s side of the series is less settled. Garrett Whitlock and Justin Slaten are on the IL, and the listed TBD for Monday leaves the opener open-ended while the club sorts through how to cover the game. The Diamondbacks, meanwhile, keep moving through a schedule that includes Merrill Kelly against Ranger Suarez on Tuesday and Brandon Pfaadt against Payton Tolle on Wednesday at 4:10 PM ET on NESN.
Kelly’s turn is the most uncomfortable part of the matchup for Arizona. He returned to Arizona after half a season on the Texas Rangers in 2025, but his ERA is north of 5.00 across 22 starts, and he has gone about 5.0 innings in each of his last five outings. In his last start he allowed six runs in 5.0 innings, and he gave up five runs in 5.0 innings the start before that. Arizona still has to lean on him in a race it cannot afford to drift from, even with the numbers suggesting he has not yet settled back in.
Brandon Pfaadt brings a different kind of profile to the series finale. In his fourth major league season, he has 61 strikeouts in 92.2 innings and has allowed 24 walks, with opponents from both sides of the plate doing relatively little damage. Ketel Marte is hitting.251/.315/.448 with 21 home runs, and Corbin Carroll has flipped from a.611 OPS in July to a.976 OPS in August, which gives Arizona a more dangerous look behind a staff that still has questions to answer. The Red Sox enter the series needing a stop to their slide; the Diamondbacks enter needing wins that keep the Wild Card math from turning against them.
The opener is the unresolved piece. If Boston names its starter before first pitch, the series immediately becomes a clearer test of whether the Red Sox can reset at home or whether Arizona can use a shaky week from the other side to stay within reach of the postseason field. If not, Monday starts with Bratt and a blank opposite him, which may say as much about Boston’s current state as any lineup card could.
