They were second for most of the campaign but a 2-1 reverse against Armenia on Friday and 1-0 loss to the Czechs on Tuesday left Bulgaria, who have not reached the World Cup finals since 1998, in fourth place, nine points behind Group B leaders Italy.
However, Bulgaria coach Luboslav Penev took heart from his side's performances and was encouraged by the local support.
"The team performed well despite the defeats in the last two games," former Atletico Madrid and Valencia striker Penev said. "We should be proud of these guys and I want to thank this perfect crowd."
Some 35,000 turned out at the Vasil Levski stadium for the game against the Czechs, compared with only 1,000 for the 1-0 home defeat by Wales in their final Euro 2012 qualifier.
"I am convinced that the full stadium is the assessment of the fans," said Penev. "They supported the team frantically for 90 minutes and this is an accurate indicator of what's been done. This assessment is very important for me."
"Our biggest success is that we were able to bring fans back to the stadium," said Bulgarian Football Union president Borislav Mihaylov.
Local pundits believe one of Penev's biggest problems was that some of his key players, including goalkeeper Nikolay Mihaylov, midfielders Stanislav Manolev and Georgi Milanov and striker Aleksandar Tonev, are not regulars for their clubs.
After Tuesday's match, Nikolay Mihaylov said he may leave Serie A team Hellas Verona in the January transfer window if his prospects of playing in the first team do not improve.
"I'll leave the club in the winter if I'm not a regular by this time," Mihaylov, who has 28 caps, told reporters. "I'm 120 percent sure as there are other options for me,"
The 25-year-old joined Verona from Dutch side Twente Enschede in August but has been unable to command a regular place with Brazilian keeper Rafael playing in all seven league matches so far this season.