(MENAFN - Muscat Daily) Oman paid a heavy price for its inefficiency in front of the goal as it lost to two-time champion Qatar 1-2 in a Group A match of the 21st Gulf Cup at the National Stadium on Tuesday.The defeat left thousands of fans and coach Paul Le Guen shell-shocked and pushed the team into a must-win situation in its concluding league match against arch rival UAE on Friday.Substitute Mohammed el Sayed tapped in a cross off a free-kick from Hassan al Haidous three minutes from the final whistle to give Qatar its first win of the tournament after it had lost to the UAE in the opener.Khalfan Ibrahim had earlier opened the account for Qatar when he converted a spot-kick in the 55th minute after the teams were locked in a goalless stalemate at half-time.Oman equalised through substitute Hussain al Hadhri in a similar manner in the 71st minute.The first penalty came when a shot from Qatar's Khalfan Ibrahim appeared to have hit the hands of Oman's Mohammed al Mussallami inside the box. Striker Juma Darwish won the other penalty, for Oman, 15 minutes later despite minimum contact with Qatar's Ibrahim Majed inside the penalty box.The result overshadowed the domination of a clinical Oman in the first half when Le Guen's team seemed to have erased the disappointing memories of its dull draw against Bahrain on Saturday.Qatar has to thank its goalkeeper Qasem Burhan for some excellent saves in that period, starting from the third minute of the match. Burhan ensured that his team was able to absorb the pressure emanating from Oman's regular raids.Both teams opted to make four changes from the squad that played the previous matches. Le Guen brought in strikers Abdulaziz al Miqbali and Darwish along with captain Fauzi Basheer and Eid al Farsi in the midfield in place of Imad al Hosni, Ismail al Ajmi, Ahmed Hadeed and Yaqoob Abdulkareem. Qatar's coach PauloAutuori fielded Marcone Amaral in defence and included Abdelaziz Hatem, Younis Ali in the midfield and Yousef Ahmed in attack. Out went Bilal Mohammed, Wesam Rezik, Mesaad Ali and Lawrence Quaye.Oman's Miqbali functioned as a single attacker with Basheer and Darwish just behind him. Eid al Farsi, Raeed Ibrahim and Ahmed Mubarak Kanu' operated in the midfield and Oman's attacking intent was clear from the kick-off.Oman earned its first corner-kick in the first minute of the match and a minute later had its first shy at the goal. Hassan Mudhaffar was involved in a one-two with Basheer on the left flank before the former send a nice cross into the centre of the rival goal area. Raeed Ibrahim timed his leap perfectly, but failed to direct the ball into goal.Bolstered by the early raid, Oman became more prolific in its attacks and operated like a well-oiled machine. However, its goalkeeper Mazin al Kasbi nearly committed a blunder soon after the first goal-scoring move when he threw the ball feebly to Mohammed al Mussallami. But Qatar's Yousef Ahmed couldn't latch on.Basheer missed another chance soon after when he broke through the defence, but his feeble shot was saved by Burhan. Then, Eid al Farsi's long-ranger nearly got a goal for Oman in the 15th minute, but Burhan tipped it over with a dive.With the match heading into the interval, Miqbali had the best chance of all but with only Burhan to beat, failed to do so.Soon after the interval, Oman found the net only to hear the whistle for Miqbali's off-side position. A few minutes later, Qatar scored and despite Le Guen bringing in Hosni and Hadhri, Oman failed to do justice to its good work on the field. UAE storms into semisManama, Bahrain - The UAE underlined its credentials as one of the favourites to clinch the title when it defeated hosts Bahrain 2-1 in a Group A match to become the first team to qualify for the semifinals with its second successive victory.The UAE had defeated Qatar 2-0 in its opening match on Saturday. On Tuesday, Ali Ahmad al Hajri got the first goal for the UAE, capitalising on a defensive lapse to score in the 40th minute.Bahrain drew level in the 76th minute through substitute Abdulwahab al Malood, but a late strike from the UAE's substitute player, Majed Hassan, in the 85th minute guided the team into the semifinals, with a match remaining against Oman.The win put the UAE on top of Group A with six points with two wins from two games, while Qatar is at second with three points after its win against Oman.Oman and Bahrain are on one point each with the final round of group games on Friday.