It’s an odd experiment going on in the middle of the Twins infield.

Brendan Harris was the closest thing Tampa Bay had to a regular shortstop last season — he played a bit more than half their innings at the position — and he was, by any defensive metric I’ve encountered, the worst in the league.

It appeared during spring training that the Twins knew that. He played a few innings at short early on in exhibitions, then was pointed at second base.

That made sense. The vast majority of major league second basemen are failed shortstops.

What you don’t encounter are shortstops who are failed second basemen. Shortstop is the more demanding position. If you can’t handle the defensive demands at second, you’re not going to handle the demands of shortstop.

The decision last week to shift Harris from second to short is partly rooted in the injuries that have put the Twins original shortstop options (Adam Everett, Nick Punto and Matt Tolbert) on the disabled list. Indeed, right now the best alternative to Harris would be Alexi Casilla, and off last season, he also could be described as a failed second baseman. But Casilla is younger, faster, with a better throwing arm. His tools lend themselves to shortstop more obviously than do Harris’.

But Harris-at-short is also rooted in Ron Gardenhire’s sense that Harris is more comfortable on that side of second base.

Eyeballing shortstops is probably more art than science. Back in 1982, Earl Weaver was pretty much the only man in the game who thought Cal Ripken Jr. could play short. It took more than a decade to move him back off the position. Around the same time, the Twins traded for a minor league shortstop of whom the word was that he might have to move to third base. Greg Gagne turned out to be the most reliable shortstop the franchise has had in its 45-plus seasons in Minnesota.

More recently, two different franchises won World Series playing David Eckstein there, and he practically has to wind up to get the ball to first base. Harris, for now, is the shortstop. One of two things will happen: Either he’ll convince Gardenhire that he belongs there, or there’ll be a ready slot for Punto when he returns from his rehab assignment.

Santana revisited

Johan Santana lost Thursday for the Mets. He’s now 5-3 with a 3.36 ERA. This isn’t bad but is hardly the Sandy Koufax-like numbers a lot of people expected from him in the National League.

Of course, we Minnesotans know that Santana is seldom at his best before Memorial Day, or even the All-Star break, and 5-3, 3.36 at this point was basically what we got over the years.

But apparently the Mets are growing concerned about his fastball velocity. He isn’t reaching the mid-90s any more. The diminished fastball makes his change more accessible to hitters.

This is what we saw last season.

The Mets doubtless expect the Santana of 2002-06; they may have the Santana of 2007 instead.