Can you guess which star's autograph this is?

Professional athletes are masters at repeating the same motions over and over in exactly the same way. That's how pitchers throw strikes and basketball players knock down shots. Nowhere is this skill more clearly on display than when they're signing autographs -- despite looking like they're scribbling mindlessly on random objects, MLB stars all generate nearly identical signatures every time.

But the ability to generate identical signatures every time doesn't mean those signatures are ever legible. We've all spent hours staring at a cap, baseball or index card, trying to figure out whose signature that could be. Before long you're asking yourself whether that's an M or a T, even though those letters should look nothing alike.

Now it's time to find out if those hours of squinting have paid off. Below, you'll find pictures of 20 baseballs signed by current MLB players -- all have made at least one All-Star team, with one exception. Some are legible. Others are, um, less so. Let's see if your authentication skills are up to snuff.

If the quiz isn’t displaying, click here.

Want more quizzes and trivia challenges? Check out the archives.