June 18 (Reuters) - Luis Romo's second-half winner sent Mexico into the World Cup knockout stage as Group A winners, but the co-hosts' 1-0 victory over South Korea owed more to opportunism and defensive resilience than attacking fluency.
Javier Aguirre's side have opened the tournament with two wins, secured top spot with a game to spare and ensured their knockout campaign against a third-placed team will begin in Mexico City on June 30.
On paper, it has been a perfect start. On the pitch, it has been more complicated.
Romo broke the deadlock in the 50th minute after South Korea goalkeeper Kim Seung-Gyu collided with teammate Lee Gi-hyuk and spilled a cross into the midfielder's path, leaving him with a simple finish from the centre of the box.
The goal was greeted with relief as much as celebration after a first half in which Mexico struggled to turn possession into clear chances and Romo acknowledgedthe struggles.
"I don't think we played a perfect game, but we won and that's the most important thing – the fans will be happy," he told Mexican TV.
The hosts started brightly at Guadalajara Stadium, but South Korea grew into the game and sections of the home crowd booed the Mexican players at halftime.
Mexico played with greater authority once ahead, with Raul Jimenez nearly adding a second from close range and substitute Obed Vargas forcing Kim into a sharp low save from distance.
Aguirre acknowledged the performance had been short of fluency, while pointing to South Korea's organisation.
"It wasn't a great match, but the opposition didn't let us do much either," he said.
Mexico's most decisive moments came in defence.
Captain Edson Alvarez, filling in at centre back after Cesar Montes' suspension, produced an acrobatic goal-line clearance to deny Son Heung-min before the South Korea captain was flagged offside.
Late on, Mexico goalkeeper Raul Rangel preserved their lead with a remarkable double save from point-blank range as South Korea pushed desperately for an equaliser.
Those interventions underlined both Mexico's resilience and their vulnerability.
They were organised, committed and ruthless enough to punish an error. But they were also short of rhythm in the final third and needed defensive heroics to protect a lead created by a mistake rather than a sweeping attacking move.
The hosts are through, unbeaten and headed for a home knockout tie. They are also still looking for a sharper cutting edge if they are to progress deep in the tournament.
(Reporting by Angelica Medina in Mexico City, Editing by Ken Ferris)
