John Jaso is, as things stand now, a role player in the major leagues.  Bobby Abreu is on the lip of baseball's Hall of Fame, having 53 of 50 points on the HOF Standards test and 94 of 100 points on the HOF Monitor test.  Still and all, scouts use "prototypes" to give a sense of a playing style.  Danny Hultzen pitches in Cole Hamels style.  James Paxton pitches in Mark Mulder style.  John Jaso is, right now, playing in Bobby Abreu style.

Abreu has something of a topspin swing, giving him a moderately high groundball rate, yet with home run capability and lots of line drives.  Jaso has the same.  Here is MLB.com's video of an August 11, 2011 base hit in which the topspin on the ball makes it sit down in front of Endy Chavez.  

Two pictures of that swing.  Here is the throughswing, with the bat going from low to high to low again:

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And here he comes back down on the finish, with the tennis-type groundstroke motion that Raul Ibanez has used to such great effect:

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Similarities:

You've got uncommonly strong men with short arms, who work the strike zone very well, who come through the hitting area with Thome-type bludgeon effect, and yet who topspin the ball rather than lofting it in Thome style.

For those just joining us, the biggest thing about Safeco being a pitcher's park, is a wind that comes in from the water, cutting across the outfield from LF to RF.  It puts a "floating" effect under the baseball, as Mike Cameron first described.  Topspin hitters like Ibanez and Sexson defeat this "floating" effect.  Jaso is also in line to be an uncommonly well-tailored Safeco hitter.

Dr. D thought he saw a declerated bat in 2011, but if so, it ain't there now.  And as Jaso lets the bat fly, Dr. D stares longer and longer at that 59:39 EYE ratio in 2010.  And the physical tools don't hurt his case none, either:

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=== Jay-Z Dept. ===

The interesting question here would be what did Zduriencik know, and when did he know it.  

Jaso had a miserable year in 2011, but that was just his second year.  Two years, one superb, one awful, and baseball (TM) took the most recent year.  The prognosis was by no means obvious, but Z went out and grabbed this one with both hands.  Did things like topspin factor in for Jay-Z?  Did he see something in the swing that could be fixed?  Or what?

Jaso looms as a possible Gillickian nab for Zduriencik.  There ain't a lot of lefty backup catchers who win you games with their bats.

In any case, the lefty topspin swing (aimed at the hole between 1B and 2B), the BB's and the OBP, everything adds up to an ideal #2 hitter.

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Come June 1, Montero's going to have a CERA way below Olivo's, and John Jaso is liable to be a plus hitter in the AL.  It will be interesting to see how married the ballclub is to Miguel Olivo.