Colombia manager Jose Pekerman has admitted that his side struggled to compete against Japan after losing Carlos Sanchez to a red card early on in the 2-1 defeat.
Los Cafeteros played with 10 men for 87 minutes after Sanchez blocked Shinji Kagawa's shot with his arm in their opening World Cup fixture.
Kagawa piled on further misery by netting the resulting penalty, but Colombia dug deep and levelled for more than half an hour through Juan Quintero's free kick.
Pekerman's charges were second best throughout the second half, however, and could have few complaints when Yuya Osako headed Keisuke Honda's corner past David Ospina in the 73rd minute.
"It is tough to lose a player so early, especially one so important," Pekerman told reporters when asked about the decisive early call from referee Damir Skomina.
"Despite that we came back in the second half. But with Japan having an extra player, it was very hard to recover possession."
Sanchez's red card was the second-quickest at a World Cup, timed at two minutes and 56 seconds.
