Simmons is unquestionably one of the best defensive players in the game, and could easily be argued to be the best defensive shortstop in the game. I think it's kind of impossible to compare him to somebody like Yadier Molina though. I don't mean Molina is obviously better or worth more, I just mean catcher is such a unique position and so hard to quantify because he's doing a whole shitload of things -- hidden, subtle, or in plain sight -- that nobody else on the field ever does.
Also though, I think Jose Iglesias has an argument that he's as good defensively as Simmons, so here's some of his most incredible plays cuz who doesn't love defensive highlights.
He was injured all of last season, but he's back this year and is apparently completely healthy.
He doesn't have nearly as strong an arm as Simmons (although it's not bad), but his hands and his footwork and his range and his smoothness and most of all his quickness are just incredible. One of the plays I link to below I've watched maybe 30 times since he did it and it still looks impossible every time.
Of course we're both literally showing our bias (Iglesias is on the Tigers now but came up with the Red Sox and was just insane for us defensively in the minors and the majors and I totally fell in love with him). But who doesn't love a bunch of incredible defensive highlights?
Jose Iglesias:
This is the impossible one. "Oh no Iglesias, you didn't just do that!"
This one is so fucking beautiful. It's also a little impossible. The Tigers' radio play-by-play call (included in that video partway through) is brilliant, and I love how he references one of the most famous play-by-play call in baseball history. I mean Iglesias fooled the entire stadium on that play. "Nobody can run that fast and put the glove down in that position, it makes no sense."
Here's a pretty fantastic compilation of his highlights with the Red Sox, including a lot of minor league highlights. I've never seen anybody release the ball as quickly as he does.
Also I really love the soundtrack. I love hip-hop but never really listen to stuff like that (club music or whatever), but it's fucking funny and has so much swagger with that highlight reel.
Then he didn't play at all in 2014 due to injury.
He seems to be back to full health or close to it. He's only played in 148 major league games in his career because he's young and he missed an entire season (also he's not a very good hitter), but if he's healthy I think he'll be making some jaw-dropping plays this year.