MANCHESTER, England, Sept 2 (Reuters) - Grimsby Town's unforgettable League Cup second round triumph over Manchester United ( MANU ) has come with a 20,000 pounds ($27,018) fine for fielding an ineligible player.

Fourth-tier Grimsby stunned United by eliminating them on penalties after a thrilling 2-2 draw in normal time last week. However, the EFL said on Tuesday that midfielder Clarke Oduor, who had joined on loan from Bradford City the previous day, was registered one minute past the 1200 BST deadline.

Grimsby reported the error themselves, saying the breach was unintentional.

"The registration of Oduor was submitted at 12:01 due to a computer issue, which wasn't immediately spotted," the club said in a statement. "We accept the fine and fully recognise the importance of following competition rules."

The club must pay 10,000 pounds now, with the remaining 10,000 suspended until the end of the season.

"We acted swiftly and transparently, and we're committed to the highest professional standards," the club said.

Grimsby face Championship side Sheffield Wednesday in the third round.

($1 = 0.7402 pounds)