Brock Lesnar may have shocked the world by reintroducing himself to the WWE Universe during Raw SuperShow on Monday, but did he rattle the Superstars looking on from the locker room as well?

They all saw Lesnar emerge at AmericanAirlines Arena and level John Cena moments later with a vicious F-5. ( PHOTOS | VIDEO) Lesnar’s intentions for his return remain unclear, as does the explanation for why he chose to resurface during Cena’s concession speech to The Rock following their “Once in a Lifetime” clash at WrestleMania. Whether he chose to send a message to the WWE Universe or simply the Cenation leader remains to be seen. ( READ MORE)

However, some of the other Superstars watching from a safe distance on Monday may also see an opportunity to rekindle old rivalries against the former WWE Champion – while others could look to start new ones. Certainly, the potential to put such a powerful presence in his place could entice a few competitors to try and boost their own reputations at Brock’s expense.

Lesnar’s actions will likely put him in Cena’s sights in the coming weeks, but who else might rise from WWE’s competitive ranks to clash with Lesnar if Brock truly is back in WWE?  WWE.com examines five other worthy contenders who could pose a formidable challenge to the man once labeled as "The Next Big Thing."

Big Show

With the classic dynamic of an immovable object meeting an irresistible force, Lesnar and Big Show collided on several occasions in the early 2000s. Reprising that colossal rivalry is surely on the wish list of any fan. What makes a present-day match between these two giants even more intriguing is the fact that Show has cultivated devastating knockout power, his WMD, in Lesnar’s absence.

The only caveat about this rematch might be for the WWE ring crew, which will need to reinforce the ring, should these two go nose-to-nose again: In 2003, Lesnar famously superplexed Show off the top rope, collapsing the ring upon impact. ( WATCH)

Sheamus

Sheamus may lack familiarity with Brock Lesnar’s past exploits as The Celtic Warrior only made his WWE debut in 2009 - nearly five years after Lesnar's last WWE appearance.

However, the reigning World Heavyweight Champion can more than make up for that deficiency by relying on his superior skill set and sheer strength. Sheamus only needs to reference his quick knockout of Daniel Bryan at WrestleMania XXVIII to prove he can match Lesnar’s brute force. If Great White can level Bryan with ease, then he can muster the muscle to clobber Lesnar.

Randy Orton

Predestined for wrestling greatness, Lesnar and Randy Orton were both fingered early in their training in WWE’s talent development program as naturals for the squared circle. Lesnar, backed by a lengthy resume of amateur wrestling titles (chief among them, the 2000 NCAA heavyweight championship), transitioned seamlessly into the professional ranks. For Orton, a third-generation Superstar, championship glory seemed almost a birthright.

Although Orton and Lesnar crossed paths during Lesnar’s first WWE tenure, the shaggy-haired Orton of 2002 bore little resemblance to The Viper of today. No shortness of grit, the young Orton at the time undeniably lacked the killer instinct that has since come to define him. Is that added element of remorselessness – informed by a decade of ring time and numerous championship encounters – enough to make Orton a credible opponent for Lesnar?

Kane

As Brock Lesnar left his last WWE match to date at WrestleMania XX, he may have noticed an unmasked Kane being humbled in the ring as The Undertaker extended his undefeated streak at The Show of Shows to 12 in a row.

That meager misfit bears little resemblance to the masked monster tormenting Superstars like John Cena and Randy Orton these days. The Devil’s Favorite Demon can summon the hellish power to handle Lesnar after proving in recent months that the monster within is alive and well.

Mark Henry

Only a rare breed of Superstar seems to take as much pleasure in dishing out pain as Lesnar does. However, Lesnar may have a peer in the form of Mark Henry.

The Freak and The World’s Strongest Man locked horns during Lesnar’s first run in WWE, and each time out, Lesnar’s farm-grown muscles put Henry’s Olympian strength to the test. The key difference between then and now is the transformation that has since overtaken Henry. Now gatekeeper of The Hall of Pain, Henry has whetted his appetite for inflicting punishment. Does this make him all the more formidable of an opponent for Lesnar, whose familiar calls of “Here comes the pain" still echo throughout the WWE Universe?

Who did we miss? Other than Cena, which Superstars would you like to see try their luck against Brock Lesnar? Comment below or take to facebook.com/wwe now and join the discussion.