Wigan won the FA Cup for the first time in its 81-year history by beating big-spending Manchester City 1-0 on Saturday in one of the biggest final upsets the tournament has seen. Ben Watson headed in the winner in the 90th minute at Wembley Stadium from Shaun Maloney's corner after City, six minutes after City defender Pablo Zabaleta was sent off. "The boys were fantastic and they deserve it," Watson told the BBC. "To come on and score the winner in the FA Cup final is a dream." Wigan now has to make sure it doesn't become the first team to win the FA Cup and be relegated in the same season, with Roberto Martinez's side currently in the drop zone with just two rounds remaining. "It's unbelievable. It's some achievement for everyone in the club," midfielder James McCarthy said. "Now it's down to the league. It's a massive week for the club. We have to put on a massive show for the rest of the season." The team, which is based near Manchester, was put together for less than $30 million, while City's squad cost more than 10 times than amount. Wigan is the second history-maker this season at Wembley, with Swansea winning its first major trophy in the League Cup final in February. "Today it was David and Goliath," Martinez said. "It was following a dream ... we saw the underdogs play with incredible bravery, incredible belief and they defied the odds again. That's the FA Cup." Wigan was led out onto the pitch by chairman Dave Whelan, who now has happier memories of Wembley after his playing career ended here when he broke his leg playing for Blackburn in the 1960 final. "What an incredible story," Martinez said. "The chairman broke his leg in 1960 and today, finally, it's finished business for him." But the result throws into doubt the future of both managers. Martinez, already widely admired in management, will be in demand even more — especially with Everton looking to replace Manchester United-bound David Moyes. At City, Roberto Mancini's future in the dugout is also looking uncertain after a newspaper report, which the club has not denied, that Malaga's Manuel Pellegrini has been approached to replace the Italian. City fans made their feeling clear toward the club's Abu Dhabi hierarchy, chanting in support of Mancini from the start and bellowing abusive about Pellegrini. But City will now end the season without a trophy despite having the most expensively assembled squad in England. The FA Cup enabled City to end its 35-year trophy drought two years ago, but despite going on to win the Premier League last season, the club has appeared to go backwards this campaign. The Premier League trophy was conceded to Manchester United with four games to go, while City exited the Champions League in the group stage for the second successive season. And on Saturday, City was outshone by Wigan. Belying their lowly position in the Premier League, the Wigan players started with confidence, looking assured on the ball. "We are playing against an incredible, incredible side," Martinez said. "Today wasn't about winning by a bit of luck — today was start to finish an incredible performance." The finishing lacked venom, though, until the final minutes — even though the team created chances from the start. Arouna Kone burst forward after nine minutes and sent the ball forward to Callum McManaman, who miscued his shot and missed the target. The closest City came was Joel Robles sliding out to block Carlos Tevez's shot after David Silva cut the ball back to the Argentina striker. McManaman, who caused City defender Gael Clichy trouble throughout down the right flank, worked his way into the penalty area again before halftime, forced Joe Hart off his line and found the space to shoot, but was denied by Zabaleta's block. "At halftime we were all really down as we thought we had played really well in the first half," Martinez said. "There was a real feeling of maybe we had wasted our opportunity, but this group of players keep on fighting." In a second half lacking clear-cut chances, Joel blocked a header from City substitute Jack Rodwell, and Maloney hit the top of the crossbar. Wigan's breakthrough came after Zabaleta became just the third player to get sent off in an FA Cup final, when he was shown a second yellow card for bringing down McManaman.