Mahrez tries to find space at Turf Moor.
City still hold a five-point cushion in the Premier League's top half.
Puel's men can get back to winning ways against the Saints next week.
The Foxes had a mountain to climb after going 2-0 behind inside 10 minutes.
Vardy provided another reminder of his abilities in front of goal with a brilliant finish.
Kasper Schmeichel and Ben Hamer
Choudhury continues to impress for the first team squad.