Conor McGregor UFC
Conor McGregor speaks during a press conference for UFC 229 at Park Theater at Park MGM on October 04, 2018 in Las Vegas, Nevada. Isaac Brekken/Getty Images

Conor McGregor is the most popular fighter in MMA, but that doesn’t mean he’s the best. The former UFC lightweight champion is an underdog as he tries to win back his title.

McGregor has +130 betting odds heading into Saturday’s UFC 229 main event, per Bovada.lv. Khabib Nurmagomedov is a -160 favorite to defeat the Irish fighter and retain the 155-pound belt.

The odds could very well change by the time the fight officially begins late Saturday night at Las Vega’ T-Mobile Arena. The betting public is usually on the side of McGregor, and the former two-division champion has been favored in almost all of his bouts.

The one exception came at UFC 194. McGregor was a slight underdog, even though he had -105 odds to defeat Jose Aldo, according to OddsShark. Aldo had been unbeaten in the UFC and was the only UFC featherweight champion in history. McGregor needed just 13 seconds to knock out Aldo and win the 145-pound belt.

Nurmagomedov isn’t only undefeated in his UFC career—the 30-year-old has never lost a professional MMA fight. He’s a perfect 26-0 with 16 wins by knockout or submission. His last victory came by unanimous decision over Al Iaquinta at UFC 223 on April 7.

It’s been nearly two years since McGregor fought inside the octagon. He defeated Eddie Alvarez via second-round knockout in the main event of UFC 205 on Nov. 12, 2016 as a -195 favorite. McGregor was a heavy underdog last year when he lost to Floyd Mayweather in his first professional boxing match.

Perhaps McGregor could be affected by ring rust since it’s been so long since his last MMA fight. It’s been 23 months since he last fought in the UFC, and now he’ll be taking on one of the world’s best pound-for-pound fighters.

Facing the best is nothing new for McGregor. It is unfamiliar territory for Nurmagomedov, who doesn’t have the most impressive resume in terms of opponents. Nurmagomedov won the UFC lightweight championship by defeating Iaquinta only after interim champion Tony Ferguson and UFC featherweight champion Max Holloway were forced to drop out.

McGregor is 9-1 in his UFC career. He’s 8-0 at either 145 pounds or 155 pounds, and only one of those fights didn’t end in a knockout. In his two fights with Nate Diaz at 170 bounds, McGregor lost by submission and won by majority decision.