In deals like this, the PTBNL would likely not be anything more than a fringe prospect; more likely, a small amount of cash will change hands.
With the addition of Alex Avila, Victor Caratini will likely be optioned to Triple-A Iowa where he can play most every day until the end of the Triple-A season and then be recalled when big-league rosters expand. Caratini appears close to big-league ready, but not quite there, and another month of Triple-A experience won’t hurt.
To make room for Wilson on the 25-man roster, one of the relievers will have to go, and the most likely candidate is Justin Grimm, who’s had an up-and-down season. More importantly, Grimm has an option remaining so can be sent down without having to clear waivers. Grimm spent much of August 2016 at Iowa, too, but was recalled and wound up pitching in all three rounds of the 2016 postseason.
Wilson, who has been closing for the Tigers, will serve as Wade Davis’ principal setup man and, since he has closing experience, is insurance of a sort if the Cubs do let Davis go in free agency. It also gives the Cubs the ability to shorten games by having two guys who have that sort of closing experience.
The deal also gives the Cubs three lefthanded relievers. Last year’s team also had three lefties in the pen in Mike Montgomery, Travis Wood and Aroldis Chapman, which gave Joe Maddon quite a bit of flexibility. This will do the same, although Wilson will likely serve more of a traditional eighth-inning setup role.
Avila will give Willson Contreras a breather from time to time; there are 58 games remaining. Figure Avila starts maybe 10 or 12 of those games, and could be used as a pinch-hitter at other times, since in an emergency Kyle Schwarber could catch a few innings here and there.
This was a very good trade for the Cubs as they are still in win-now mode and gave up one player who was blocked at the big-league level and another who’s probably four years away from the majors. In return they got two players who are having fine years and can help them right now.