Undefeated in seven MMA bouts, McMann earned a silver medal in women's freestyle wrestling at the 2004 Olympics. The former wrestler has been billed as Rousey's toughest stylistic matchup.
Rousey secured a bronze medal in judo at the Olympics and has gone on to become the face of women's MMA. Utilizing her judo roots, Rousey has submitted all eight adversaries she's faced since going pro less than three years ago.
Which Olympian will claim the women's bantamweight crown at UFC 170 on Saturday in Las Vegas?
Here is a closer look at how Rousey and McMann match up in all areas.
Rousey and McMann have both been able to remain undefeated by simply using what got them to this level.
While Rousey's coach, Edmond Tarverdyan, would have everyone believe Rousey could beat a world champion in boxing right now, the women's bantamweight titleholder hasn't really showcased that high-level striking inside the Octagon.
In her defense, Rousey hasn't had reason to stand for extended periods. She owns a huge advantage over most female fighters on the ground, and she's held onto her belt by submitting foes on the canvas.
What Rousey has displayed is a pretty good jab, which could be useful should McMann use her wrestling to keep this fight standing.
With even fewer MMA fights than Rousey, McMann's striking is also still in the developing stages. In recent fights, she's mostly moved straight forward with two-strike combinations. Unless she shows some serious improvement at UFC 170, McMann could have her advances shut down by Rousey's jab.
It's hard to imagine this fight being decided by striking. If it somehow is, though, Rousey should be able to land more frequently than an opponent who throws with more power than technique despite still being in search of her first standing knockout victory.
At UFC 168, Rousey put on a judo clinic, throwing Miesha Tate to the canvas six times in less than three rounds.
In her throws, the champion has some of the most effective takedowns in the women's bantamweight division. However, on Saturday, Rousey will meet the best female wrestler to ever enter the Octagon and quite possibly the only fighter in the 135-pound division capable of beating her when it comes to takedowns.
McMann put her wrestling on display in her UFC debut, taking Sheila Gaff down twice in less than one round en route to a ground-and-pound win. The world-class freestyle wrestler has also already shown the ability to shut down judo techniques and counter them with takedowns of her own.
At ProElite 3, Hitomi Akano repeatedly attempted a koshi guruma against McMann. However, the American recognized the throw immediately, sunk her hips and dumped Akano onto her back to score several takedowns.
Notably, McMann finished most her takedowns in that matchup by landing in half-guard or side control. It will be important for her to do the same against Rousey, who would be forced to regain full-guard before she can threaten with armbars.
Rousey has been able to toss other opponents around the Octagon. She won't be able to do the same against McMann, who should have an edge in takedowns. Whether going to the ground will be a smart decision for McMann could be another story.
With eight armbars in eight professional bouts, Rousey has successfully established herself as the most dangerous grappler in women's MMA.
All her opponents have known the armbar is coming, but none have found a way to shut it down. Until her recent rematch with Tate, Rousey hadn't even seen an opponent who was able to survive one round before being submitted.
McMann has never tapped, though. While she has only had one UFC appearance, McMann has also survived on the ground with some skilled submission artists.
Shayna Baszler has scored 14 of her 15 MMA victories via submission. Akano had an excellent armbar of her own, securing 10 over the course of her career. However, neither of those women were able to submit McMann despite spending plenty of time on the ground with the Olympian.
That said, McMann did find herself in some compromising positions against those two opponents in bouts that only lasted three rounds. Defending armbars over five rounds against a submission specialist like Rousey might prove an impossible task on Saturday.
It has been nearly 10 months since McMann last stepped into the Octagon.
That is a long break heading into any matchup. Heading into a five-round championship bout with Rousey, a layoff that long could end up being very detrimental.
In a rare occurrence, Rousey is also the more experience fighter. In addition to having one more fight under her belt, the champion has competed in several title fights now, while McMann might be dealing with more pressure in this matchup than she has heading into any contest in her athletic career.
Before Rousey's rematch with Tate, many could have made the argument that McMann had an advantage in conditioning. However, Rousey was able to answer some questions by stopping Tate in the third round, so any edge McMann might have in conditioning probably won't be significant at UFC 170.
McMann has the wrestling that will likely be needed to dethrone Rousey.
Though, wrestling will likely need to be utilized in reverse against Rousey, who continues to catch adversaries in her patented armbars no matter how much they prepare to defend against them.
McMann is capable of keeping this fight standing, but she hasn't developed into a better striker than Rousey, who has appeared to improve more quickly in that area. If standing is even included in McMann's game plan, she'll be forced to abandon it should she have trouble working inside Rousey's jab.
While McMann may be the one to take this fight to the ground, Rousey can finish from anywhere once she's on the canvas.
Rousey defeats McMann by submission in the third round.
Statistics via FightMetric.com.