The Croatian, on loan from Real Madrid, has registered no goals and just one assist for the west London club.
It is unclear whether Chelsea will try to make Kovacic's deal permanent at the end of the season. And the 24-year-old knows he must do more to convince the club of his importance.
Kovacic told the Evening Standard: "Of course, I want to improve. That's a part that's missing in my career so far, the goals and the assists.
"But I'm not watching myself so much. I'm occupied with my team, that the team performs at its best and I give the best.
"In the end, who scores or gives the assists is not the most important thing for me, but I have to improve a lot in this aspect."