Of course the guy isn't what he used to be, and was probably robbed of a few good years by concussions, but he still has plenty of value. He's become an excellent defender at 1B. Probably Gold Glove caliber. He's not going to win any Silver Slugger awards, but he's still doing some things well at the plate. There seems to be some outrage with him batting behind Sano, but I think it's a solid strategy in terms of helping Sano get some pitches to hit. Mauer is still respected enough by opponents, and still handles the bat at a level that deters pitchers from simply walking Sano every time. If you take a guy who you know is highly susceptible to strike outs (much more so than Mauer, which is basically everyone in the team), and I think it's a little easier to justify putting Sano on first base.