Mexico and South Korea were forced to settle for a share of the spoils in a lacklustre Group B opener at the Olympics on Thursday.
The Koreans were the more dominant of the two sides but, with the exception of skipper Koo Jacheol's glancing header, were restricted to long-range efforts by Tena Luis Fernando's side in a game that never threatened to spring into life.
Mexico came close to snatching all three points in the dying seconds, as second-half substitutes Giovanni dos Santos and Raul Jimenez both spurned gilt-edged opportunities.
Meanwhile, Switzerland and Gabon drew 1-1 in the second match of Group B to put all four sides in the group on a single point after the first round of games.
Switzerland took the lead inside five minutes when Admir Mehmedi converted a penalty won by Innocent Emeghara, but the goalscorer missed an excellent chance to extend the lead after 20 minutes.
Gabon however improved after a poor start as Pierre-Emerick Aubameyang became a clear threat, equalising just before half-time after good work from Alexander N'Doumbou.
The second half saw the Swiss reduced to 10 men as Oliver Buff received a second yellow card for diving, but the European side managed to hold on for a point and remain level with their Group B opponents.