Yes, it's possible. Your player will not gain experience as fast as he should.
Most probably he is a free youth player that somebody just sold.
But don't give up on him yet, I have a slow trainer in my team who always performs very well, second best player actually, and I don't mind that his level is 6 below my team average, he is simply that good (best ever on assisting and second place on scoring - he's an MC).
Check his performance during a couple of days and then make a decision.