"I don't subscribe to that. First and foremost, both are on long-term contracts, so their contribution was always envisaged as far more than just one season," he said.
"Have we see the best of Shevchenko and Ballack? No. Did they contribute positively? Yes, and they have continued to do so in ways that people may not have expected.
"For example, not only did Shevchenko score goals - which he did, though lots of people think he didn't score one! - but also the benefit he provided for Didier Drogba was significant.
"Ballack played an awful lot of games for us. The experience both players brought to the club off the pitch people don't see. We haven't seen the best of them but I'm confident we will."