#2 Rollins already called Brock out on WWE RAW
With RAW's ratings being low in December 2018, some fans may actually have missed this moment but Seth Rollins actually called out Brock Lesnar on WWE RAW.
On the December 10th, 2018 episode of WWE RAW, Rollins called out Baron Corbin for doing a terrible job as the RAW GM. While listing all of Corbin's terrible decisions as General Manager, Rollins also buried his decision to "hand" the title back to Lesnar.
Rollins also added that the champion was never actually on the show and also that the last time Lesnar had actually wrestled on RAW was way back in 2002.
After that promo, Rollins has to be the one to face Lesnar. He's already called out Brock and even though fans may have forgotten it, it has set up this feud perfectly.