In return, St. Louis received BOS No. 19 prospect Blaze Jordan (1B) as part of the deal.
Matz currently has a 3.44 earned run average through 32 games this season. The 34-year-old lefty has given up 21 earned runs on 56 hits through 55 innings, striking out 47 and walking just nine batters.
Matz's 1.18 WHIP is a career-best throughout his 11 years of service in the MLB and will now look to give a boost to a Red Sox bullpen that already ranks fourth in all of baseball with a 3.37 ERA.
Jordan is having a dominant year in the minors this season. He's slashing a total .308/.377/.495 between Double-A and Triple-A (.298/.341/.480) with a total of 12 home runs and 62 RBI in 88 games.
The 22-year-old Jordan gives the Cardinals a very promising young prospect who could see time in a Cardinals uniform sooner rather than later.