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.
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.
"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.