Paul Heyman believes the key to Brock Lesnar and Roman Reigns' success is because neither of them are ever content with what they've achieved.

This Sunday Brock Lesnar will defend his Universal Championship against Roman Reigns at WrestleMania. While it hasn't been officially announced, it is highly likely that the two of them will main event the show, much like they did three years ago at WrestleMania 31. If that does happen it will be Reigns' fourth WrestleMania main event in a row, and perhaps Lesnar's last.

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The discussion about which match should go on last has been raging on for a while now but ultimately that decision is down to one man, Vince McMahon. That's why the Lesnar - Reigns match will almost certainly be the one that headlines Sunday night's show. McMahon has a certain affinity towards both Superstars and recently Paul Heyman gave an insight as to why that might be.

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The advocate spoke with NBC Sports about a number of things relating to the professional wrestling scene today and naturally the topic of his Beast came up quite a lot. Heyman pointed out that Reigns and Lesnar are never 'content'. That many other wrestlers would treat being in the main event at WrestleMania as the culmination of all their hard work and that they have achieved what they set out to do. The Beast and The Big Dog on the other hand see it as another opportunity as to why they should be used and pushed even further.

via wwe.com

According to Heyman Vince McMahon has that exact same mentality. 'At 72 years old he's launching a football league in two years and that's not all he's going to be doing. I'm sure Vince is looking for other projects. That's just who he is. Vince McMahon is not done carving out his legacy', Heyman explained to NBC. Despite being a billionaire and the owner of WWE he is still not content.

Heyman quite rightly pointed out that when a WWE Superstar is content that's when they stop ascending up the card. Only the performers that see each step as an opportunity to demonstrate to the boss why they should be promoted even further are the ones that will make it to the very top of the industry. That's why the angle between Lesnar and Reigns is the top one in the company right now in the eyes of Mr. McMahon.