When Nolan Arenado was a prospect, no one really knew he’d be a five-time All-Star, four-time Silver Slugger and eight-time Gold Glove Award winner. He was a second-round pick in 2009 who didn’t make our Top 100 list until 2012, and scouts weren’t sure could play third when he entered pro ball.

The point in bringing up Arenado’s humble beginnings is to show that you never know just who prospects might become in the future. That includes the quartet of prospects the Rockies got from the Cardinals, along with lefty Austin Gomber, for Arenado in the deal that was officially announced on Monday: third baseman Elehuris Montero, shortstop Mateo Gil and right-handers Tony Locey and Jake Sommers.

Before discussing the prospects, it’s worth noting that Gomber provides present value to the Rockies’ big league staff. The left-hander topped out as the Cardinals’ No. 14 prospect prior to the 2018 season, when he went 6-2 with a 4.44 ERA across 75 innings in 29 games (11 starts) in his big league debut. He didn’t pitch in the big leagues in 2019, dealing with arm issues, but returned in 2020 and pitched very well for St. Louis, posting a 1.86 ERA across 29 innings in 14 games (four starts). With a good curve and an average fastball and changeup, his ceiling might be limited to a No. 4 or 5 type starter in that role, but he could be very dependable coming out of the bullpen as well.

As for the prospects, Montero is the highest-rated of the bunch -- currently at No. 7 on the Rockies’ Top 30 -- has the highest upside and is the key to this deal. Is the big corner infielder the guy who hit .315/.371/.504 across two levels of A ball in his full-season debut, largely as a teenager, in 2018? Or is he the overmatched hitter who managed just a .562 OPS in Double-A in 2019?

To be fair to Montero, who will play most of the 2021 season at age 22, he missed large chunks of 2019 with injuries, including a broken left hamate, as he struggled with the large leap to Double-A. There’s a lot of offensive potential to unlock here, with a very exciting combination of bat speed and strength that points to a lot of power. He’s a free swinger, something that got exposed by more advanced pitching in the Texas League, as he saw his strikeout rate jump from 19.4 percent in 2018 to 30 percent the following year. He hasn’t played in a game since the Arizona Fall League in 2019, though he did participate at the Cardinals' alternate training site last summer. He needs more reps to refine his overall approach, but he still has the ceiling to profile as a run-producer in the big leagues.

Whether he can stick at third long-term remains to be seen, but the Rockies do have options at the hot corner up and down the system. If Montero has to move to first, so be it, because in the end, it’s his bat that will determine his value. He has the chance to individually make this trade seem a lot better if he can get back to the hitter who broke out in 2018.

Locey, coming in at No. 15, has two ingredients all systems covet in pitchers: size and arm strength. He can touch 98 mph with his fastball now and triple digits could be in his future depending on his role. His hard slider gives him a second above-average pitch, and he also has a decent curve in his arsenal. His changeup is far behind the other offerings as he didn’t need it at the University of Georgia.

The right-hander both started and relieved with the Bulldogs, with his work in the rotation in 2019 helping him land in the third round of the Draft that June. He pitched sparingly during his summer debut in the Cardinals’ system, only in relief, showing the ability to miss a ton of bats (16.4 K/9) and walk a lot of hitters (6.4 BB/9) in a small sample size of 17 innings.

And that’s what will determine Locey’s ultimate role and value. Most feel he’ll likely end up in the bullpen because of his issues with repeating his delivery and throwing strikes. But he’s big, strong and durable and maintains his velocity deep into outings, so it’s too early to pull the plug on him starting. And there are many big league starters currently on Major League rosters who had “reliever risk” tags on them when they were prospects.

Gil also has a differing ceiling and floor and while the former is somewhat limited, the latter is pretty high. His father Benji spent parts of eight years in the big leagues and won a title with the Angels in 2002, which certainly doesn’t hurt. The feel for the game that comes with growing up around it is part of what makes the Rockies’ current No. 22 prospect’s floor so high. There’s some certainty Gil will be a big leaguer, even if it’s in a utility role similar to what his dad did for the Rangers and Angels.

The biggest aspect of Gil’s game that adds to that certainty is his ability to play shortstop. He has an above-average arm and above-average defensive actions. There is no question he’ll be able to play the premium position defensively at the highest level. It’s in his bat where the ceiling lies for the 20-year-old infielder. He has excellent contact skills and has already added some strength and made strides offensively since the Cardinals took him in the third round of the 2018 Draft. He’s yet to really play above the Rookie-ball level, but he did show some ability to drive the ball in the Appalachian League in 2019. If his right-handed bat keeps developing, then you’re looking at a starting shortstop.

A quick note on Sommers, the one guy not on the Top 30 as a senior sign who is likely to be a reliever. He might seem like a throw-in, but his power fastball-slider combination gives him a chance to impact a big league bullpen eventually.

Will all four of these new Rockies reach their ceilings? That’s probably unlikely. But it’s not out of the question and the collective upside of this quartet is why it pays not to evaluate this trade until several years have gone by.