MLB betting: Diamondbacks have been biggest surprise, best bet so far this season

Before the Major League Baseball season, one team was a favorite of two prominent projection systems. Baseball Prospectus' PECOTA and Fangraphs both had the Arizona Diamondbacks significantly above their win total at BetMGM.

The computers look smart so far. A little more than a month into the MLB season, the Diamondbacks are the most profitable team for bettors. That's a surprise.

According to Covers.com, which tracks how much bettors would be up or down if they bet $100 on each team in each game, the Diamondbacks have been the most profitable in baseball and by a good amount. They've made a solid $688 profit for that hypothetical $100 bettor. The New York Mets are second on that list with a $530 profit.

Bettors who had Arizona on their radars because of the preseason projections are happy so far.

Diamondbacks playing better than expected

Before the season, the Diamondbacks' win total at BetMGM was 65.5. Arizona had the biggest positive discrepancy between its PECOTA projection and BetMGM win total. PECOTA had the Diamondbacks at 72.9 wins. Fangraphs wasn't quite that high but still had the Diamondbacks at 70 wins. No other team had a projection at least four wins above its BetMGM win total at both projection sites.

There was good reason BetMGM's total was so low. The Diamondbacks were 52-110 last season and even 65 wins would have been a massive improvement. Arizona also plays in the NL West, and that's a lot of games against some really good teams.

So far Arizona has been way ahead of expectations. They're 15-14, which isn't incredible on the surface. But bettors are cashing in because Arizona is often an underdog and usually with a big number. If you're willing to take a big underdog, you've cashed some nice tickets betting Arizona.

D-Backs bettors have already pocketed a nice profit. Now they have to wonder if Arizona can keep it going.

Can Diamondbacks keep it up?

If there's one way the Diamondbacks might stave off regression, it's with better luck on balls in play. The Diamondbacks' batting average on balls in play (a simple stat that tells a story of whether a player or team has been lucky or unlucky) is a league-worst .232. Only one other team is worse than .260, and that's the Houston Astros at .249. If the Diamondbacks' luck turns their offense will be even better. It's hard to believe their BABIP will remain anything near .232.

The bad news is the Diamondbacks' pitching has been lucky. Their xFIP at Fangraphs (expected fielding independent pitching) is 4.33, third-worst in MLB. That's a full run above their ERA of 3.33, so some regression is coming.

The Diamondbacks do have a tough strength of schedule remaining — fifth-hardest according to Tankathon — but ESPN's RPI says Arizona has already played the toughest schedule in MLB. It's not ideal to play a schedule that tough, but the Diamondbacks are used to it.

There's some concern about the bottom falling out for Arizona and its bettors. The Diamondbacks are far ahead of expectations, there are a lot of tough games coming up and there should be some regression in pitching.

But Arizona has been quite good to bettors so far, and that's worth keeping in mind when you see the Diamondbacks catching a big number.