Rudra hated the intelligent type of opponents the most.
He could easily take on a dumb tier 5 existance and give the man a run for its money if he could invite him into falling for his tricks one after another. However the intelligent kind did not fall for such stuff.
Mahrez was the intelligent type of opponent that was calm and surveyed his surroundings and his enemy intentions well before making a decision.
Such an attitude made it hard for Rudra to make a battle strategy that could skew the innate disadvantage of having a lower level into an advantage.
Rudra did a bit of mental calculation and understood that in terms of stats he should be at par or only slightly inferior to Mahrez at the moment as upon reaching tier 5 from 4 one would get all stats doubled.
Unless Mahrez was a freak of nature and had naturally boosted stats , he should be about par with Rudra.