Despite leaving Nadir Ciftci, Stuart Armstrong, Andrew Robertson and Gary Mackay-Steven on the bench, United competed with the champions until the latter stages of the game at Celtic Park.
McNamara has the Scottish Cup final to look forward to next week against St Johnstone, and he reckons his charges are well prepared for the return to Celtic Park.
"The focus is on next week but I thought it was a professional performance," the former Celtic defender said.
"I am not too disappointed. I thought we passed it well and were well organised.
"We left a few of the more forward players on the bench. You have seen the craft of Mackay-Steven and Armstrong when they came on."