Minor League Mondays: Could Jonathan Santucci Be The Mets' Next Lefty Starter?

The trade of David Peterson this past week created an opening in the Mets' rotation from the left side. For the better part of the past 15 years, the Mets have at least one steady left-handed starter in the back of their rotation. The line of succession has gone from Jon Niese to Steven Matz to Peterson, with many assuming Zach Thornton could be the next in that line. One other man who could fill that spot is Jonathan Santucci, who is the focus of this week's edition of Minor League Mondays.

Binghamton lefty Jonathan Santucci is one of the Mets' top pitching prospects.

Santucci, 23, was the Mets' second round pick in 2024 out of Duke, coming to the organization in the same draft class as Carson Benge. A high walk rate in his final year with the Blue Devils caused Santucci to slip to the second round, where the Mets gave him full slot value to join the organization. The Mets held Santucci's debut until 2025 and he pitched well, going 9-4 with a 3.05 ERA in 25 appearances (including 23 starts) between High-A Brooklyn and AA Binghamton.

Santucci was sent back to Binghamton to repeat the level to start the year and got out of the gate slowly, causing some concern as he went 0-3 with a 5.71 ERA in April. The Mets also saw Santucci start slow in 2025 before he righted the ship and the same trend has happened this season. Santucci has been much crisper since the start of May, currently checking in with a 3.95 ERA in 14 starts, taking his ERA down nearly two full runs over the last two months.

That workload has covered 66 innings for Santucci, who has compiled an 80:34 strikeout to walk ratio in that span. Opponents are hitting just .227 against Santucci, who has been utilizing a solid pitch mix of a fastball that sits between 92-95 miles per hour and a devastating slider. Figuring out a third pitch that can effectively get hitters out, such as improving his changeup or slider, could be the key to Santucci being a solid major league starter.

Scouts are high on Santucci, who is currently the Mets' seventh-best prospect according to MLB.com, and feel that his existing combination of pitches should be enough to give him a floor in the back of a big league rotation. Exceeding that ceiling would require development of a third pitch that he can use to get hitters out, which should be Santucci's focus over the next few years.

If Santucci continues to excel with Binghamton, the next step would likely be a promotion to AAA Syracuse within the next month or so. That could come as a result of a Mets' sale at the deadline that could see Freddy Peralta and Clay Holmes moved to contenders, which would create big league rotation spots for Thornton and some combination of Jonah Tong and Jack Wenninger.

Even though it isn't likely Santucci could get big league innings this year, the ripple effect of those moves would create an opening in the Syracuse rotation for him. The target for Santucci to be big league relevant would appear to be next summer, although time will tell if he or Thornton has a better shot at being a home grown lefty to join the Niese line of succession as a Mets' lefty.