Nemanja Matic scored the only goal of the UEFA Champions League encounter in the 34th minute, but failed to build on that advantage despite dominating the first half.
Sporting had goalkeeper Rui Patricio to thank for thwarting a number of one-on-one situations, while the home side's attacking threat was limited for the most part.
Despite Chelsea's inability to make the lead more comfortable, Mourinho felt the result - and not the winning margin - was most important in the group stage.
"It's not a knockout where goals are fundamental, it's points, and these are three points," he said.
"I think the game was hard but correct. The referee controlled it so everything was okay."
Chelsea now top Group G, two points clear of Schalke and Maribor who are tied on two.