Im not sure where people are getting "mediocre" when describing Gay's defense. Memphis was the 8th best defensive team 2 years ago, 5th best last year and #1 this year. Gay plays 37 mins a game, surely he's a big contributor to Memphis' defense since he plays heavy minutes. And his individual DRating is 105, 102 and 99 respectively. compared to lebron who was 102,97 and 103, who plays the same position and has been considered numerous times for DPOY.
This is actually my selling point with Gay, the ability to handle the ball in the crucial seconds of the game, something that the Raptors have been lacking for quite sometime, and which i think is a skill highly underrated and undervalued. You need a guy who can do this.