Ancelotti, who viewed Beckham as a possible alternative to Andrea Pirlo as a deep-set playmaker before he arrived on loan from Los Angeles Galaxy, has the chance to test out his theory against Serie A's bottom club with Pirlo suspended.
However, he is wary of embarking on tactical experiments with a player in such good form.
"Beckham can play in a central position but (Mathieu) Flamini can (too) and that's why I tried it," Ancelotti was quoted as saying by La Gazzetta dello Sport after Wednesday's 2-2 draw at Glasgow Rangers in a friendly.
"Beckham has found a good equilibrium on the centre-right and I think it's best not to move him."
Beckham, who has said he would like to stay with Milan on a permanent basis, has scored twice in five Serie A games and set up two goals in the 3-0 win at Lazio on Sunday that lifted his side into second place, six points behind Inter Milan.
Attention at the San Siro will also be focused on whether Ancelotti opts to leave Brazil playmaker Ronaldinho out of his starting lineup for a fifth consecutive league game.
Champions Inter will be aiming to put some inconsistent form behind them at Lecce earlier on Saturday, when midfielder Sulley Muntari will be available after suspension.
Forward Adriano is serving the last game of a three-match ban for throwing a punch against Sampdoria last month but Dejan Stankovic is being tipped to play after coming off with a knock in Sunday's 1-1 draw with Torino.
Juventus are seeking to end a run of two successive league defeats, which caused them to slip to third, at Catania on Sunday.
Last season's runners-up AS Roma, who are sixth, entertain fourth-placed Genoa on Sunday in a match between rivals for a Champions League qualification slot.
