Ex-Manchester United and Tottenham striker Sheringham told Prime Casino: "I used to work hard, play hard in my day, but you still need to know when to play hard. There have always been players over the years that worked OK and played hard, and their football abilities fell off a cliff. Jack's a little bit in that mold at the moment. They won the treble, and he celebrated, and it doesn't seem like he's got back into his football mode yet. He needs to, otherwise his career might slip away. He's had a couple of injuries, I know he has, but it's amazing how easy it is for a football career to slip away. He needs to get his focus back again and make sure that he gets back in the Man City team and stays free of injuries. To do that, you have to do the right things at the right times. I think he needs to get his focus back on football and everything else will fall into place."