Newcastle were guilty of giving the ball away cheaply in the middle of the park and Wilfred Ndidi fed the Algerian.
Despite picking the ball up almost on halfway, Mahrez is a constant danger and he showed his quality by driving forward and leaving Isaac Hayden for dead.
With the goal now in his sights, Mahrez had only one thought in his mind and he duly fired past Karl Darlow from 25 yards.
It was a fine strike and a timely reminder of Mahrez's undoubted quality.
Check out the goal for yourself below:
What a goal #Mahrez pic.twitter.com/c4vDugMxPs
— ian (@IANPAM7) 9 December 2017