Turner wasn't outjumped by Chopra, if you look at the footage again, you'll see that Turner went towards the front post to help cover and the ball went to the back post, nigh on landing on Chopra's head, with Chopra barely having to jump for the ball at all!
Turner tried to get back to the far post, but only jumped up on the line, to try and stop Chopra's effort from going in, without directly competing for the ball with Chopra!
If Turner can be blamed for the goal in any way, it's for leaving Chopra alone in the first place!
I've no idea how he played at Peterborough, but Turner was very good against Ipswich and IMO, he was superb against Barnsley!
I'm not getting carried away with Turner though, as he's only played 3 full games for us, but I'm very impressed with his contribution so far!