The Thai champions had begun the 2012 ACL with back-to-back wins but were eliminated on Tuesday with their coach apologising for their failure
The result ended Buriram's 2012 campaign which started off so brightly after back-to-back wins in their opening two matches against Kashiwa Reysol and Guangzhou, before finishing with four consecutive defeats.
"I'm sorry we have failed in an important mission tonight but the players, coaches and staff have given their best," Buspakom told reporters.
He added: "The turning point was when we lost to Jeonbuk twice, once at home and once away. We suddenly felt the pressure then to bounce back and reclaim out points."
The Thai club already were eliminated following Kashiwa Reysol's 2-0 win at Jeonbuk Motors earlier in the evening but Buspakom insisted they didn't pay attention to the result and pushed for the win against Guangzhou.
"In the second half we had more attempts on goal but we just couldn't convert," Buspakom said.
"We didn't pay any attention to what was happening in any other game. It's always our mission to win for the Buriram United fans, especially at home."