It's been widely reported now that the Tampa Bay Rays are expected to move Tyler Glasnow this offseason, and the Cardinals' interest in Glasnow is also well known.
While teams typically take their time when shopping high-end talent like Glasnow, a major part of the Rays' motivation to move on from Glasnow is to free up money from their payroll this offseason. If they want to use any of that money to go after free-agent targets, then they'd ideally have a deal in place sooner rather than later.
A lot of talk has been about the Cardinals jumping the market in terms of landing an early free agent, but they could do the same thing through the trade market instead. For St. Louis, acquiring Glasnow in the next week checks one top-end starter off their to-do list and allows them to narrow down their focus a bit more with other potential free agents and trades, having a better idea of what their budget would be.
I also think the Cardinals are uniquely positioned to pull this off while other teams may not want to pull the trigger yet. Teams like the Dodgers and Braves, who have also been linked to Glasnow, likely want to see what the markets for Shohei Ohtani, Aaron Nola, Yoshinobu Yamamoto, Blake Snell, and Sonny Gray look like before making quick decisions, and the Cardinals could take advantage of that.
Glasnow's trade value is really hard to pin down, but I provided three updated trade packages recently coming out of the GM Meetings. The Rays won't be able to ask for a ton in return for him, but I would imagine an MLB-ready bat like Alec Burleson, Tyler O'Neill, or Dylan Carlson plus a pitching prospect would be the basis for a deal. Tommy Edman could even be used in a swap as well.
The Rays are going to want to replenish their pitching staff through free agency like other clubs, so freeing up cash immediately so they can go after guys like Michael Wacha, Seth Lugo, Eduardo Rodriguez, or whoever they see as a fit would be huge for their offseason plans.