JoJo Romero is not the only Cardinals' reliever opposing batters should worry about

The St. Louis Cardinals were not expected to do much this season. They got rid of some key contributors over the offseason to fully focus on the rebuild. 

However, this rebuild is off to a way better start than nearly anyone could have imagined. They have gotten off to a 14-10 start, which puts them right in the thick of things in the NL Central. 

The problem is, no team in that division has a losing record. In fact, the Milwaukee Brewers sit at the bottom with their 13-11 record. 

MORE: Cardinals' high-pressure success has them surging in latest power rankings

JoJo Romero is not the only Cardinals' reliever opposing batters should worry about

A large portion of the team's success is coming off the bat of Jordan Walker. he leads the team with his .292 batting average, eight home runs, while Alec Burleson leads the team with 17 runs batted in, and Ivan Herrera leads the team with his .387 OBP. 

But you can't get wins without a solid level of pitching, and St. Louis has gotten it. And while the starting rotation is doing its part, it is the bullpen that is turning heads. 

JoJo Romero is a great high-leverage arm that opposing batters are aware of. But maybe not Riley O'Brien, who is dominating as the team's closer. He has seven saves with a 0 ERA. 

If it wasn't for Mason Miller, O'Brien could be stealing the show. Either way, he has made Bleacher Report's Joel Retuer's list of the biggest surprises so far.

"He handled some high-leverage duties down the stretch last season after Ryan Helsey and Phil Maton were traded, finishing with a 2.06 ERA and 8.4 K/9 in 42 appearances. Now he's closing games for a better-than-expected Cardinals team and pitching like an All-Star Game shoo-in."

If you don't know his name, you should get familiar with him now. He will be an arm that the fanbase hopes will make it past the trade deadline later this summer.

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