The England international joined the Blues on a season-long loan from the Red Devils last summer.
As part of the deal, the club agreed a conditional obligation to buy him for £25 million if they finished 14th or higher in the league.
The Blues are obliged to purchase him as things stand, but there is a penalty clause. Chelsea can bow out of the purchase agreement by paying a £5 million fee to United.
When pressed on Sancho's future today, Maresca said: "I'm not thinking at all about next year or the players that can be here next year.
"I'm just thinking how we can get the best from them to finish the season very strong."
Sancho scored a sublime goal from the edge of the box against Ipswich Town last weekend. He will be aiming to continue the recent good form.