Boston Red Sox
Another team in desperate need of starting pitching, much like the Cardinals, is the Red Sox. Their offseason was similar to the Cardinals' in that neither team addressed their rotation holes. Boston let Michael Wacha and Nathan Eovaldi walk in free agency.
With that being said, Boston's major bright spots in the rotation have been James Paxton and Brayan Bello. I would imagine that neither of those starters are going anywhere at the deadline, especially not Bello. But Montgomery could be a fit in Boston.
Despite sitting in last place in the AL East, the Red Sox are still very much alive in the Wild Card race. Montgomery could reunite with Paxton, who was a teammate of his during his time in New York, and give the Sox a chance to gain some ground as they look to rebound from a disappointing finish in 2022.