Concerns over Joe Mauer's defense has grown exponentially as the number of opposing kleptomaniacs have continued to accumulated more and more bases.

A one-time Florida State quarterback recruit, earlier in his career Mauer had thwarted over 30% of would-be base-stealers but has seen that number drop to league average as injuries and age have taken a toll on him. This year, however, that rate has dropped to a league-worst six percent – stopping just three runners with his own arm. What's more is that the opposition's appetite to motor on the basepaths has increased significantly too.

Prior to yesterday afternoon's matinee against the Mariners, Associated Press reporter Jon Krawczynski relayed on Twitter that manager Ron Gardenhire said that Mauer's caught stealing decline had nothing to do with his arm, rather the source of his struggles had to do with his slow slidestep when positioning for a throw down to second.

Meanwhile 1500ESPN.com's Phil Mackey provided further details of what the manager was seeing in his All Star catcher:

Reviewing the limited MLB.com archive video clips available of Mauer throwing down to second, there definitely is evidence of what Ron Gardenhire was speaking towards Mauer's mechanics.

The first clip is over Mauer attempting to throw out Maicer Izturis of the Angels. Liriano's fastball is up in the zone and gives Mauer a good chance at nailing the trailing running in the double steal but the throw skips into center field when Alexi Casilla cannot handle the hop.

The next clip is Mauer throwing out Detroit's Brennan Boesch – one of three times he has done so in 2012. Now, Boesch is not much of a base-stealing threat so it is possible that Mauer was caught flat-footed because of that but, just like in the clip above, Mauer is on his heels and stands straight up then pivots his feet.

Now compare Mauer's current form against a couple of examples from his past. This first clip is from 2010 in which Mauer nails the Royals' Chris Getz in his attempted thievery. Note how he starts to slide his backside out before receiving the pitch, getting his body into the throwing position.

Similarly, in this 2008 matchup between the Twins and Padres, Mauer nabs Jody Gerut at second and slides his backfoot/backside into a position while receiving the ball rather than waiting on the ball to come to him before getting into the throwing position.

Essentially, Mauer's footwork is costing him valuable nanoseconds and, quite likely, some mustard on his throws down to two as well. And opposing teams and their stopwatches and scouts are clearly picking up on this – which is why they are averaging nearly a stolen base attempt in each of his games behind the plate. That is a huge increase from his younger days.

With no clear-cut explanation for why he has been tardy with his footwork, it is hard to determine how this affects this Twins. Obviously, the injury to his knee -- which may have played a role in a slow start at the plate this season -- may still be lingering. In that case, it could be a financial disaster for the Twins who are paying him to be an elite up-the-middle defender in addition to his offensive contributions. Then again, it could simply be the rust of having not played catcher as regularly. Either way, as Gardenhire said, it will be almost impossible to get this repaired in-season.