#3 Seth Rollins vs Brock Lesnar
Most would probably say that Seth Rollins winning the men's Royal Rumble was a foregone conclusion. Since the departure of Roman Reigns, many have believed that Rollins would be the obvious choice to be 'the guy' on the RAW brand and being 'the guy' would lead to Seth taking on Brock Lesnar at WrestleMania.
So if this prediction seems a little too obvious, let's take it a step further and predict the outcome. Seth Rollins will win the Universal Title with the help of Roman Reigns.
Prior to the Royal Rumble, there were rumours that Reigns might be making an appearance. He's not yet cleared to wrestle but thoughts were that he might just show up in a non-wrestling role.
If he is currently well enough to make an appearance, what condition will he be in, come WrestleMania? Even if he isn't cleared to wrestle, Reigns' music hitting and him walking out to the ring may be a big enough distraction to allow Rollins to get the upper hand and pin Brock Lesnar.