Inter Milan boss Walter Mazzarri admits Mateo Kovacic has surprised him this season.
The midfielder struck in their 1-1 draw with Palermo yesterday.
Mazzarri said: "He had an injury and didn't train for three or four days, so he wasn't sharp at the end and I had to substitute him. He has improved so much this season and is scoring regularly, which he'd never done before.
"I honestly did expect Kovacic to make this step up, as it was only a matter of time. We must all realise that the same players cannot play every three days for 90 minutes at full tempo. We have to all train well and keep mentally and physically alert to share out the resources."
