The prolific Cristiano Ronaldo scored the only goal of the game on Wednesday to ensure Real won UEFA Champions League Group B with a game to spare.
Ronaldo's 26th goal of what is proving to be another stellar season was enough to give the European champions a 15th consecutive win, matching the achievements of the Real teams in the 1960-61 and 2011-12 campaigns.
Gareth Bale struck the crossbar and Ronaldo spurned a golden opportunity to score his 72nd Champions League goal in the second half to ensure the Portugal forward is three goals adrift of new record holder Lionel Messi.
Ronaldo's first-half goal drew him level with Real legend Raul's tally of 71 goals in Europe's premier club competition and Ancelotti was able to reflect on another victory, but knew his side had failed to match the high standards they have set.
The Italian said: "We have not played as we always do, a little slower, but good defending and we were concentrated. The most important thing was the victory."
Basel remain in second place and only need to avoid defeat against Liverpool at Anfield to join Real in the last 16.
Ancelotti is backing the Swiss champions, who had their chances to equalise in the second half, to go through.
He said: "Basel played with a lot of heart. They showed an intense game and could therefore put us under pressure in the second half.
"I think Basel is currently better than Liverpool. I see a small advantage for Basel for the last round [of matches]."
