Bulgaria gave new coach Lothar Matthäus a winning start as Ivelin Popov scored the only goal in Cardiff to bring their UEFA EURO 2012 qualifying campaign to life after defeats in their first two Group G games.
Popov struck three minutes after half-time to put a smile on the face of a Bulgarian team showing five changes to the XI who started last month's home game with Montenegro. The tall striker showed a sure touch, skilfully guiding a right-wing cross away from James Collins before firing in off the right-hand post.
It was a devastating blow to Wales who were also under new management, with Brian Flynn beginning a two-match spell as caretaker boss following the departure of John Toshack. That switch followed their own defeat to Montenegro in the opening fixture; a second reverse with games against Switzerland and England next on the agenda, casts Wales' qualifying prospects in a poor light.
In a lacklustre first-half only a handful of chances were created at either end of the field. Wales almost scored after seven minutes when Gareth Bale and Joe Ledley combined down the left. Steve Morison cleverly left the ball for the onrushing Chris Gunter whose shot flew hard and true but centimetres the wrong side of the post.
The visitors retaliated when a mistake allowed Martin Petrov a clear sight of goal. The response from goalkeeper Wayne Hennessey was exemplary as he palmed the ball over.
Following Popov's goal, Wales' search for an equaliser foundered on a well-drilled defence though Morison did force a fine save from Nikolay Mihaylov. With a minute of normal time remaining, debutant Hal Robson-Kanu got on the end of Bale's inswinging cross but could not keep his header down. In added time Gunter capped a miserable night for the Welsh by receiving a straight red card following a foul on Dimitar Rangelov.