Daniel Murphy uses relief pitcher's bat

Stickers on bat knobs, such as the ones the Mets use, easily display when a player uses someone else's bat. Gordon Donovan

Last summer I wrote about how MLB teams are increasingly using numbered decals on bat knobs, instead of using the old-school method of writing the player's number on the bat knob with a Sharpie. The trend has actually picked up steam since then with more and more teams using the decals.

One interesting byproduct of this is that it's now much easier to see when a player is using another player's bat. For example, Mets second baseman Daniel Murphy has been mired in a month-long slump that's seen his average drop from .331 to .275, and he's apparently been trying out different bats in an attempt to regain his stroke. Two weekends ago he was using relief pitcher Tim Byrdak's bat, and this past weekend he tried Jason Bay's bat -- a desperate measure, given Bay's chronic woes at the plate.

But switching bats isn't limited to players who are scuffling. Nats rookie phenom Bryce Harper has been tearing it up (Saturday's 0-for-7 notwithstanding), but that didn't stop him from using teammate Tyler Moore's bat the other day.

Stuff like this has been going on for years -- for generations, even -- but it used to go unnoticed, because a hand-scribbled number on a bat knob can be hard to make out. Now, thanks to the bat knob decals, another element of the game within the game has been revealed to us.