"is going to come back, but his most recent procedure shouldn't be dissimilar to the last one in terms of results: he'll be okay for a while, but the time will come when the shoulder will start to tighten up. At that point, Rolen's going to have to take a hard look at a needle full of cortisone and the rest of his life after baseball."
At 33 years old Rolen is not getting any younger. He will be under control for the next 3 years at $12M a season. If he performs up to 2006 levels, the Jays made a good swap considering Rolen's defensive play (in 2006, Rolen ranked as the second highest scoring defensive third basemen as per The Hardball Times fielding Win Shares).
Troy Glaus, is a straight up masher, owning a career .246 ISO (Isolated Power). Like Rolen, and as mentioned, Glaus is an ex All Star. He is under contract for the next season with an option, that Glaus will undoubtedly accept, totaling $12M annually.
Will Carrol explains of Glaus' injury history which included his back, shoulder and most recently, feet. However, the back issue should subside with the move away from Rogers Center's field turf, the shoulder issue is a thing of the past and the Cardinals, as Will Carrol discusses, "have good experience with managing plantar fasciitis—they've been able to keep Albert Pujols on the field despite the condition, and Pujols has continued to produce due to some advanced techniques and plain old hard work."
Defensively, there really isn't anything special to say about Glaus. In 2006, Glaus was #12 in the majors in THT's defensive Win Shares (a cumulative statistic) and in 2005 he finished tied for #11, scoring a 3.8 and 4.0 respectively.
What do the experts say? Fangraphs now has the Bill James, CHONE and Marcel's projection systems posted and here is what they say about Rolen and Glaus respectively:
Bill James - .282/.367/.475
CHONE - .274/.353/.449
Marcel - .271/.342/.435
Bill James - .251/.360/.490
CHONE - .256/.364/.490
Marcel - .257/.356/.479
Keep in mind that each of these projections were created prior to the trade, given that each player changed leagues and parks, these projections could vary. But essentially, the projections are calling for a further drop off for Rolen and for Glaus to hit marginally under his career averages.
What do I think of this trade? Honestly, its all St. Louis in my opinion. Consider the following from Mitchel Lichtman's July 2006 article from The Hardball Times,
"players who switch from the NL to the AL, tend to get worse and players who switch from the AL to the NL tend to get better."