Brown's team - who were beaten on penalties by Second Division East Fife in midweek cup action - lost out to his previous employer when substitute Bob McHugh took advantage of an error to net a decisive breakaway goal six minutes from time.
Second-bottom Aberdeen have yet to win or score away from home this term, and Brown said: "I don't think we deserved to lose but I didn't think we deserved to win.
"The teams cancelled each other out in a stalemate type of game, and that's what I think the result should have been.
"We conceded a soft goal - credit to Motherwell and Bob McHugh for taking their chance and for a good substitution, but we're obviously disappointed that they scored from our corner with a breakaway.
"An individual error cost us and that's been the case in one or two games, and we've had very little good fortune.
"Motherwell hit the bar twice but that's the first time anyone's done that against us this season - we've hit the bar five times and the post twice, when we make an error we get punished, and we haven't had any good fortune at all.
"I thought our performance was solid enough; there wasn't great flair about the team but it was a workmanlike, solid, conscientious display."
At the end of a difficult week, Brown insisted he did not feel under any pressure, saying: "I'm privileged to work with an excellent football club and I'm determined that we'll be getting some results in the very near future.
"I don't feel any pressure, just the same acute disappointment the fans are feeling and I'm determined to make sure they don't continue to feel that way."
Source: Team Talk
Source: Team Talk