A delighted Gambia coach Fred Osam Duodu, who has inspired his team to play without fears, said: "It wasn't an easy match at all and, as I always say, any team that reaches a tournament like this must be a very strong opponent and that was how it proved. Unfortunately one or two of my best players were out and I think that was why it was a little bit tougher for us today."
Gambia were forced into two changes from the team that famously beat Brazil in their opening match, with Lamin Conteh and George Cole coming in for the suspended Saja Leigh and Ebrima Sohna. Qatar, meanwhile, gave starts to Ahmed al Emais and the frighteningly fast Khalfan al Khalfan, who was not fit to play all 90 minutes against the Netherlands.
The Gambians were roared on by a large contingent of passionate fans from their homeland and they gave them plenty to shout and sing about in the first half as they took the game to Qatar at a frenetic pace.
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Sainey Nyassi and Momodou Ceesay both went close before Gambia forged in front. It was the impressive Ceesay who hit the target, firing home low for his second goal of the tournament and enhancing his already considerable reputation at Peru 2005 (0:1, 24').
Qatar were not to be denied though and within six minutes they scored, Yusef Ali showing a fantastic burst of speed before sliding the ball under the advancing Babucarr Suso for a somewhat surprising but delightful equaliser (1:1, 32').
It is tempting to say the Gambian fans were stunned into silence, but the truth is they did not miss a drumbeat in their encouragement and Qatar were on the back foot for the rest of the half. Ousman Sonko flashed a shot just wide for Gambia and Abdoulie Mansally brought an excellent reflex save out of Ghaith al Mohannadi, but the teams went into the break on level terms.
Fans makes their own entertainment
The second half did not match the first in terms of excitement or goalmouth incident and the spectators were left to amuse themselves with Mexican waves for sustained periods.
Qatar keeper al Mohannadi had to be on his toes to deny substitute Sanna Nyassi from close range as he almost turned a teasing cross by Alagie Ngum into the net, but as the match wore on it had the look of stalemate.
Qatar goalscorer Yusef kept their hopes up with his silky skills and jinking runs, but Gambia retook the lead courtesy of a spot-kick after Ceesay was bundled off the ball when clean through. Skipper Ousman Jallow, who netted from a twice-taken penalty against Brazil, this time required only one attempt to send al Mohannadi the wrong way (1:2, 78').
As the clock ticked down and Qatar tired, Gambia managed to match their score against the Brazilians. Substitute Pa Modou Jagne neatly grabbed the third goal (1:3, 92') before he and his team-mates took the acclaim of their ecstatic fans and went on a lap of honour to wave goodbye to Piura ahead of their third game against the Netherlands in Lima on Friday.
Qatar coach Tini Ruijs said: "I thought we were a little but unlucky with the red card because my player had only just come onto the pitch. It was his first foul and he was not warmed up or used to the pace of the game. However, we played against a good, strong Gambia team and they scored some beautiful goals. I think they deserved to win."