Assistant manager Mickey Lewis rued a lack of quality from Oxford after Macclesfield left the Kassam Stadium with a 1-1 draw.
The Silkmen went in front after nine minutes when Michael Duberry headed into his own net from Matt Hamshaw's free-kick, his third own goal in Oxford's past four home games.
Former Norwich forward Oli Johnson equalised just before half-time for the Us with a low drive into the bottom corner from 20 yards, but Oxford failed to complete the turnaround after the break.
"Our quality in the second half let us down," said Lewis. "There weren't enough crosses coming in and with Macclesfield playing deep we needed someone to take on one of their players, but no-one did.
"We've got some really good players but their form in the second half was below the standard we expect. We draw too many games at home.
"In the first half we should have made more of the opportunities we had. We started so well and were on top, they got the boost of a somewhat fortunate goal, but when we drew level with a good goal, I thought we should have kicked on from there."