(CNN) -- The so-called richest game in football hinged on a late defensive error by Derby captain Richard Keogh as Bobby Zamora scored a dramatic injury-time winner for 10-man Queens Park Rangers in the Championship playoff at Wembley Saturday.
Promotion to the English Premier League is estimated to be worth $200m and it was QPR celebrating an unlikely win at the final whistle.
Former England international Zamora scored with a first-time volleyed shot after Keogh's intended clearance fell straight to his feet.
It was QPR's first shot on target after a match largely dominated by Derby -- particularly after Gary O'Neil's red card on the hour mark.
O'Neil went for hacking down Johnny Russell as he raced towards goal and it looked only a matter of time before Derby, managed by former England boss Steve McClaren, grabbed a winner.
His QPR counterpart Harry Redknapp admitted as much as he reflected on his side's triumph.
"We were hanging on with 10 men until a fantastic finish," he told Sky Sports. "We were hanging on for our lives," he admitted.
QPR, relegated from the EPL last season, has spent heavily, backed by owner Tony Fernandes, with a massive wage bill in comparison to other rivals in the second flight of English football.
Leicester City and Burnley gained the two automatic promotion spots, leaving QPR to negotiate its passage through the playoffs involving the next four best-placed teams in the league.
Victory over Wigan saw QPR into the final, while Derby thrashed Brighton to reach the Wembley showdown.
A cagey and tactical match produced few chances, the best coming after O'Neil was dismissed but QPR's man-of-the-match defender Richard Dunne and goalkeeper Robert Green were outstanding in repulsing Derby.
Then came the late drama -- with Zamora repeating a feat he achieved in helping West Ham win the playoffs in 2005.
It left a distraught Keogh to be consoled by his teammates while QPR lifted the playoff trophy.
For McClaren it was a bitter disappointment after guiding his young team to third place in the regular season standings and a deserved place in the final.
"I've lost some games in my career but that is the cruelest," he told BBC Sport. "For somebody to make mistakes -- we don't blame anybody," he added.