On Friday, to the surprise of absolutely no one, the Chicago Cubs promoted Kris Bryant to the big leagues. With the service time shenanigans out of the way, it was abundantly clear that Bryant that he was their best third baseman, so they summoned him from Iowa to help their team win. Today, the Cubs have also pulled shortstop Addison Russell up from Triple-A, where he’ll join Bryant, Starlin Castro, and Anthony Rizzo to form something close to the infield of their dreams.

Unlike with Bryant’s promotion, however, this one didn’t appear imminent, nor has Russell necessarily forced his way into the big leagues. While everyone agrees that he’s one of the best prospects in baseball, it’s less clear that he’s finished developing in the minor leagues, and is ready to step in and produce from day one the way Bryant is. In total, Russell has just under 1,100 minor league plate appearances, and only 321 of those have come above A-ball.

He was excellent in Double-A last year, hitting for power and making contact, but his walk rate eroded, a perfectly natural thing to expect from a 20-year-old facing advanced pitching for the first time. That trend has continued in the first few weeks in Triple-A this year, as he’s drawn just one walk in his first 47 plate appearances. Of course, a middle infielder who can hit for some power and avoid striking out already does enough to justify his spot in the line-up, so even if Russell is still in the overly-aggressive phase of his development, that doesn’t immediately preclude him from being a productive player in 2015.

His ability to help the Cubs this year will likely come down to how much contact he can make against big league pitching as a 21 year old without much high-level experience. Russell is only here because Arismendy Alcantara hasn’t been able to make the necessary adjustments, turning his 23% strikeout rate in Triple-A into a 32% strikeout rate in the majors; gap power middle infielders have to put the ball in play more than that to be playable.

To Russell’s credit, his strikeout rates in both Double-A and Triple-A have been above average, and it’s highly unlikely that he’ll swing and miss as often as Alcantara. But if he has a proportional increase, and his K% jumps into the 25% range, then it might be tough for Russell to actually provide a huge boost to the Cubs. As it stands, Steamer’s rest-of-season forecast is calling for a 21% strikeout rate, while ZIPS — not yet incorporating his 2015 minor league numbers — -is at 25%. Russell is going to have to hit for above average power to be a productive player at those levels.

Of course, he very well might do that. Both systems are somewhat bullish on his present power, projecting roughly a .150 ISO from him this year; an above average mark for any hitter, much less a middle infielder. If Russell can drive the ball that often, the team can live with a not-yet-finished understanding of the strike zone. But that was the same hope they put on Javier Baez last year, and that didn’t work out so well. Russell doesn’t have Baez’s contact problems, but he is a reminder that a poor approach at the plate can invalidate just about every other offensive tool a player has.

While ZIPS and Steamer were in love with Kris Bryant — projecting him as a +4 WAR player for 2015 even before he got to the big leagues — the forecasts for Russell aren’t as rosy, painting him as something closer to a slightly below average player this year, and with plenty of risk surrounding that forecast. Jonathan Herrera provides a pretty low bar for Russell to clear, and with Tommy La Stella hurt, Russell may very well be the Cubs best option right now, but we shouldn’t put the same expectations on Russell that followed Bryant to the big leagues.

Russell is a terrific prospect, and given the Cubs second base alternatives, he may be able to make them a little bit better in the short-term, even as a guy who probably could have used more seasoning in the minors. But like Baez and Alcantara before him, there are reasons to think that this could not go particularly well, or at least, Russell has enough work to do that he may not be a big upgrade right away. That shouldn’t remove any of his future shine, or cause Cubs fans to sour on his long-term prognosis; that would be entirely normal for a player his age and with his minimal experience.

The Cubs, though, are pushing in on 2015, and it’s worth taking a shot to see if Russell is more ready than the numbers might suggest. If the talent trumps experience and he turns into a quality regular, they pick up an extremely valuable upgrade in a tight Wild Card race. It’s absolutely worth the shot, and even he flops in his first stint in the big leagues, they can always send him back to Iowa. This seems like more of an experiment than a commitment, and the payoff if it works is worth the cost if it doesn’t.

But I hope people don’t lump Bryant and Russell together simply because the Cubs called both of them up in a week’s time. Bryant didn’t belong in the minors, and might have been big league ready last summer; Russell probably isn’t there yet. The Cubs have the incentives in place to choose 2015 wins over Russell’s development, but this promotion should come with guarded hope more than the jubilant exuberance over Bryant’s arrival. It might work, it might not, and it’s worth trying, but while Kris Bryant over Mike Olt was a huge step forward for the Cubs, Addison Russell is more of a flyer. A flyer worth taking, but don’t get too bummed out if Russell is back in Iowa in a month. He’s a serious talent, but the Cubs are pushing things a bit with this promotion, and as Alcantara and Baez have shown, major league pitchers are pretty good at exploiting flaws that didn’t get polished out in the minor leagues.

Long-term, Russell is probably going to be one of the best middle infielders in the game, either at second or shortstop, depending on how their talent backlog gets sorted out. Just don’t count on him making quite that kind of impact in 2015. It might happen, but it would be the exception, not the rule.