The Cardinals on Tuesday announced that they'd placed Michael Wacha on the 15-day disabled list with shoulder inflammation. To take Wacha's spot on the roster, the Cardinals called up 21-year-old right-hander Alex Reyes, who's perhaps the top pitching prospect in all of baseball ...

Reyes wasn't previously on the 40-man roster, so to make room the team transferred backup catcher Brayan Pena (knee) to the 60-day DL. With Reyes poised to make his ballyhooed debut in St. Louis, let's run down some essentials about Reyes and another arm who's on the way ...

1. Reyes has one of the best fastballs of any prospect

Reyes regularly hits triple digits with his four-seamer, and once you see his delivery you'll rightly call it "easy triple digits" ...

That's Reyes blowing one past Clint Frazier in the recent Futures' Game. Reyes also boasts a changeup and a 12-6ish curve that unleashed upon Dansby Swanson in that same Futures Game. As you can see, the stuff is certainly there.

2. Reyes hasn't thrived at Triple-A this season

This season for Memphis, Reyes has pitched to a 4.96 ERA in 14 starts. That's obviously not optimal, even in the generally hitter-friendly Pacific Coast League. Limiting damage off the bat has been an issue this year for Reyes, as has been his control: 32 walks in 65 1/3 innings. On the other hand -- and this hints at his potential long-term -- he's also struck out a remarkable 93 batters in those 65 1/3 frames. So even with a high walk rate, Reyes has still struck out 32 percent of the batters he's faced this season. That's fairly remarkable. Also, he's registered a solid ground-ball/fly-ball ratio of 1.52. So look past the run-prevention numbers, and you see dominance.

3. Reyes is going to work out of the bullpen for now

Reyes told assembled media on Tuesday that he's going to be in a relief role in St. Louis, at least to start. That stands to reason, as Reyes' generational fastball can certainly do the heavy lifting in the bullpen. The Cards also need help from the right side, given Trevor Rosenthal's ineffectiveness and subsequent injury. This, after all, is a team that has given high-leverage setup innings to Jonathan Broxton. If Reyes earns the confidence of manager Mike Matheny, then he could work some key spots down the stretch as the Cardinals try to make the postseason. Reyes certainly has the stuff to be a lockdown reliever, but his long-term future figures to be in the rotation.

4. Another prospect is on the way to help out in the rotation

Speaking of the St. Louis rotation, there's this ...

Weaver, the 27th-overall pick of the 2014 draft, is the Cardinals' No. 2 prospect behind Reyes, and as a college arm who'll soon turn 23, he's a bit more of finished product than is Reyes. So he's in line to get at least one start, and said start will come against one of the NL's best offenses. Weaver this season has been dominant in 12 starts at the Double-A level and then very effective in one Triple-A trip to the mound. Across 83 innings in 2016, he's put up an ERA of 1.30 (albeit with nine unearned runs allowed) and a sparkling K/BB ratio of 7.67. Weaver's already got a plus fastball-changeup combo, but his slider and curve are still works in progress. Suffice it to say, if he fares well against the mighty Cubs in Wrigley, then a longer look may be in order.

4. The Cardinals' pitching staff needs help

The SportsLine Projection System presently gives the Cardinals a better than 50 percent chance of making the postseason (via a wild-card berth, of course), but if they're going to make that happen then the pitching staff needs to improve. At present, the Cardinals rank seventh in the NL in rotation ERA and fourth in bullpen ERA. The numbers aren't bad, necessarily, but we're talking about a competitive wild-card fray in the NL. Also, the Cardinals' five-man rotation has started all but one of the team's games this season, so it remains to be seen how some of those arms hold up the rest of the way (see: Wacha, Michael).

If the Cardinals are to make the playoffs for a sixth-straight season, then Reyes and Weaver will probably have something to do with it. Tuesday's news taught us that much.