Houston, June 18 -- Portugal head coach Roberto Martinez defended his side's performance and rejected concerns over Cristiano Ronaldo's goal drought after a 1-1 draw with DR Congo in their World Cup Group K opener at Houston Stadium.

Portugal took an early lead through Joao Neves in the sixth minute and appeared in control in the opening stages. However, it failed to extend its advantage and was later punished as DR Congo, competing in its first World Cup in 52 years, equalized to secure a historic point.

Ronaldo, 41, played the full 90 minutes but delivered a relatively subdued performance and was unable to make a decisive impact in front of goal. Asked whether the veteran striker should be substituted in tight matches, Martinez dismisse...