Ballack spent four years at Stamford Bridge and played a key role in persuading Schurrle, 23, to join the Blues.
He told the London Evening Standard: "It was his first season playing for a big club and it was a big challenge to go to the Premier League and for that I think he did quite well. There is still a lot of space to improve - he is still young. Hopefully he can still improve next year and can be a main player for the team.
"At Chelsea you play for the title - week in and week out you have to perform on the edge. Sometimes he scored and it was still not enough to stay in the first eleven in the next game. He has to learn to give always 100 per cent in training. He had some good performances and he had a period when it looked like Jose Mourinho didn't really want him but then he came back which was positive."
For the big stories and the banter follow us on Twitter: @tribalfootball