John Cena's epic WWE career will have its official curtain call at Saturday Night's Main Event on Dec. 13, and fans are leading up to a frenzy of speculation about his final opponent.

With a stacked tournament in full gear in honor of facing the 17-time World Champion, former WWE head writer Vince Russo has chimed in with a surprising prediction. He said that Brock Lesnar could be the final opponent who will fight Cena in his last WWE match.

The Battle for Cena's Final Opponent Heats Up

WWE Wrestlepalooza Rumors: Did John Cena Personally Decide to Lose
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According to Slam Wrestling, WWE has launched a star-studded tournament to decide who will step into the ring with Cena for his retirement match. Some of the popular wrestlers who have a shot to fight him are Bronson Reed, Gunther, LA Knight, and Solo Ikioa.

Other options are Sheamus, Carmelo Hayes, Penta, Rusev, Finn Bálor, and Jey Uso. While Gunther vs Camelo Hayes and Solo Sikoa vs Penta matches are happening soon, Russo said that none of them may get the chance to square off with John Cena.

Vince Russo Predicts a Brock Lesnar Return

On an episode of Coach and Bro via EWrestling News, Vince Russo gave one such prediction that lit up wrestling discussions online in an instant. Whereas the assumption going into WrestleMania would be to see one of the tournament finalists earn their spot, Russo believes Brock Lesnar will crash Cena's final match to take the place for himself.

"I'm still holding out that whoever wins the tournament. Brock Lesnar's going to take them out, and BrockLesnar's going to have the match with Cena. I'm still holding out for that, Coach."

If this happens, Cena vs. Lesnar would be the headliner for one final time, a colossal showdown between two of WWE's most dominant forces.

For Russo, Cena's Nov. 10 final RAW appearance in his home state of Massachusetts, headlining the show by capturing the Intercontinental Championship from Dominik Mysterio, needed far more hype and emotional weight.

Russo Says Cena's Retirement Year Deserved Better

Russo also voiced disappointment over how WWE has handled John Cena's retirement run.

He felt the creative direction did not match the level of Cena's legacy and called the buildup "sub-standard" for a superstar of that stature.