Everyone here has heard of a Super Two player. Here is the necessary criteria for becoming a super two: at least 2, but less than 3 years of service time with at least 86 days of service in the immediately preceding season. In other words, someone who has 42 days of service one year and 44 days the following year would not qualify for super two. It must be 86+ days followed by 2 full seasons. That's no guarantee he'll be a super two. Of the players that have at least 86 days of service one season followed by 2 full seasons, only the top 17% of those qualify as super two.
Teams often try to avoid this so they can pay the player less money over 6+ seasons before he files for free agency. The only way they can guarantee the player isn't a super two is if he has 85 days of service or less in one season followed immediately by 2 full seasons. This year that would be July 10th, which is the All-Star game. Any player called up on July 10th or earlier who remains on the roster the next 2 years would be eligible for super two. He probably would not qualify since it's only the top 17% in service time, but if all teams are waiting longer and longer to call players up in an attempt to avoid this, that would be the date.
If the Cubs want to guarantee themselves Brett Jackson won't be a super 2 they'll have to wait until July 11th to call him up. Realistically, they could probably call him up in mid-June and he would not qualify. Anthony Rizzo already has 68 days of service time though. If he were to get the requisite 86 days this season followed by 2 full years, he'd almost certainly be a super two. He'd have 2 years plus 154 days of service time. He'd be only 18 days shy of qualifying for 3 years of service time.
If the goal is to avoid super two status, the Cubs won't even consider calling Rizzo up before the 2nd half of the season begins on July 13th. This way Rizzo would have fewer than the necessary 86 days of service time in one season. That's also the date at which they'd officially call Brett Jackson up to gaurantee they avoid him being a super two.
Rizzo is killing the ball in AAA, but Bryan LaHair is doing the same thing at the MLB level. ZiPS now projects a .353 rest of season wOBA from LaHair. This seems more than reasonable. LaHair has become a tough player to pitch to. He can hit the ball out of te park with ease to all directions. Pitchers will have to be very careful with him and they can afford to considering the Cubs lineup. I wouldn't be surprised to see a .360ish wOBA the rest of the way.
Because of that you can't just call up Rizzo and replace LaHair. At least not if he's playing well anyway. LaHair becomes an interesting trade piece for the Cubs. If or when they call Rizzo up, the 1st base job is his. You could try LaHair in LF. He played 14 games in the outfield last year and for the 2010 Iowa Cubs he played 48 in left field, 47 at 1st and 2 in RF.
ZiPS projects a .313 wOBA the rest of the way for Alfonso Soriano so given the choice between Soriano and LaHair it's pretty easy to figure out which of the two is better. LaHair's advantage may actually be so big that platooning the two would make little sense. And if the Cubs can show that LaHair can play a decent left field, he'd have more value in a trade. Or the Cubs could be content to have a league minimum left fielder for the next couple years while they suck. They're going to have a high paid player at the position who sucks anyway.
Brett Jackson's path to the big leagues is a bit clearer. If he's hitting well by the time the MLB All-Star game rolls around, he'll probably be called up. On the other hand, he's not setting the world on fire right now. He does have a .344 wOBA and that's good for a 105 wRC+. Looking at his triple slash stats he seems much less impressive (.233/.330/.419). I hadn't followed him much since the early part of the season when he was raking so when I saw that line I was surprised. I was also thinking about how less than average it is compared to the PCL, which has had an average of roughly an .850 OPS the last few years. This year his OPS is better than average thanks to lesser hitting. In fact, the league OPS is .750 and Jackson's is .749.
Jackson has cut down on the strikeouts some, but is still at 27%. It was 29% last year at Iowa so there may be no improvement at all. The biggest difference between his overall batting numbers this year is the BABIP. Last year at Iowa he had a BABIP over .400. This year it's a more reasonable .310. Jackson's BABIP has often been in the .350s and higher. This is the lowest it's been in his career and it is a small sample to this point, but .310 is probably about the highest level we could expect from him at the MLB level.
This is why I've always said that Jackson is going to have an ugly batting average for those who care about such things. He strikes out too much that he'll have to maintain a very high BABIP in order to have a decent batting average. The good thing for him is that even with a bad batting average he's still going to be providing league average on base skills.
Right now though, he some stuff to work on before he should even be considered for a call up. The Cubs can afford to wait and they will. Jackson isn't setting the world on fire and demanding he be called up. Rizzo is crushing the ball, but Bryan LaHair is 4th in MLB in wOBA (and wRC+) among players with 60 or more PA. Rizzo's wOBA in AAA is .477 while LaHair's is .489 at the big league level. Small sample size applies, but LaHair has been better and he's done it at the highest level.
I think we'll see Brett Jackson at the start of the 2nd half and Rizzo at the end of July when Bryan LaHair is traded to a contender.