Gordon Strachan says Scotland have no-one else but themselves to blame after Wales came from behind to win their World Cup qualifier 2-1 at Hampden.
The hosts began the match poorly as a Gareth Bale-inspired Wales kept the Scots penned in their own half but a Grant Hanley header in first half stoppage time handed them the lead at the break.
A more confident start from Scotland in the second half saw them come within a whisker of doubling their advantage when Robert Snodgrass hit the post with a curling strike.
However, the match turned in the 73rd minute when Snodgrass was red-carded for a late lunge on Chris Gunter.
Aaron Ramsey hammered home the penalty before Hal Robson-Kanu headed Wales into the lead a minute later to leave the Scots shell-shocked.
Ramsey then saw red in stoppage time after he pulled down James McArthur but Scotland had no time to take advantage as they slumped to their third defeat in five games in qualifying for the 2014 finals in Brazil.
Strachan, who took charge of the national side for the first time in a competitive match, said the game hinged on the penalty and Scotland's inability to grab a killer second goal.
"The game changed on the penalty because at that point I thought we were getting better," the Scotland manager said.
"When you are 1-0 up, you have to score the second one which we had chances to do. Then the penalty caused us a problem. We were down to 10 men and they scored right away so it was an uphill fight.
"It is hugely disappointing. To get beat in any game is disappointing but with the national side that is hard to take. But we have to get on with it because it is our own fault we haven't won."
The result leaves Scotland firmly rooted to the bottom of group A with just two points from their opening five matches as their hopes of making Brazil 2014 lie in tatters. Strachan's side next face Serbia away on Tuesday and the manager says his only target now was to get some points on the board.
"We need to try and win games. It's not a good period for us," Strachan said.
The win moves Wales to third on six points, all coming courtesy of their back-to-back wins over Scotland, but they are seven points behind leaders Belgium and Croatia.
Wales face group leaders Croatia on Tuesday, which manager Chris Coleman says is a must-win if they are to keep their slim hopes of qualifying alive.
However, they might have to do it without Tottenham star Bale, who didn't emerge for the second half at Hampden after suffering an ankle knock.
"We have now got to try and beat Croatia on Tuesday possibly without Gareth Bale, Coleman added.