Norris Cole's defense is not why he's getting more playing time than Mario Chalmers in the 2014 Eastern Conference Finals.
According to mysynergysports.com, Norris Cole ranked 50th in points allowed per play this season while Mario Chalmers ranked 110th. That makes it seem like Cole is the better defender than Chalmers and thus the logical choice for Erik Spoelstra to play against Lance Stephenson in the pick-and-roll.
The problem with that thinking, however, is that mysynergysports ranks Chalmers 1st in the league in points allowed per play when defending the ballhandler in pick-and-rolls while Cole ranks 8th.
As Jason Lieser of the Palm Beach Post pointed out, offense is the reason why Cole's getting more playing time than Chalmers the last two games. Cole's shooting efficiency is 15 points higher than Chalmers in the Eastern Conference Finals and he's averaging just 0.7 turnovers per 48 minutes while 'Rio's averaging an insane 5.2 turnovers per 48 minutes. If 'Rio doesn't knock down shots and take care of the ball, he will continue losing playing time to Cole in this series. It has everything to do with his offense, not his defense.
The spreadsheet below lists the defensive stats for Cole and Chalmers from mysynergysports.