Haddad Maia, who became the first Brazilian woman to reach the top 10 in the WTA rankings after her semi-final run at Roland Garros a month ago, shot out of the blocks on a cloudy morning to convert two early breaks and take a 3-0 lead.
Cirstea could be heard urging herself to "Fight, fight, fight," and although she fought back with a break of her own, Haddad Maia attacked the Romanian's weaker second serve to break once again and serve out the opening set.
Unable to match the power of the taller Haddad Maia on long rallies, a frustrated Cirstea had animated conversations with her coach between games as she sought answers but found few solutions as the Brazilian went 4-0 up in the second set.
Backed into a corner, the Romanian finally got on the board in the second set when she induced a rare unforced error off Haddad Maia's forehand before serving to stay in the match.
But that only delayed the inevitable as Haddad Maia ground Cirstea down in her final service game and clinched victory on her first match point.
And just in time as the rain came down, the players scrambled off, and the covers came on under grey London skies.
