Failing getting Snell, Boston needs to go out and get Jordan Montgomery
Unfortunately, if Blake Snell is made available, the Padres are going to be fielding calls from most of the league. Boston has the prospects to get that deal done especially with Snell being a rental, but his price could exceed what they are comfortable with. If that happens, Boston needs to have the Cardinals' Jordan Montgomery in place as at least a backup plan.
Here is the fundamental issue: Boston doesn't need warm bodies for their rotation, they need real production and that is where Montgomery could really shine. While the Cardinals' pitching staff as a whole has been a dumpster fire, Jordan has been very good this season with a 3.37 ERA with the peripherals to match.
Montgomery may not have the upside that Snell has given that he is a former Cy Young winner that misses more bats than Jordan. However, Montgomery is a reliable strike thrower and Boston should be very familiar with him given the time he spent with the Yankees.
There are going to be few opportunities to get high-end starting pitchers at the trade deadline this year. Boston needs to at least try to get a deal done for one of them.