Unable to hold up the ball or link with Japan’s central playmaker Keisuke Honda, Kagawa was replaced by Yoichiro Kakitani in the final minutes of the Group C match.
“If this is the result, this says a lot about me,” he told reporters.
The once unthinkable prospect of Kagawa missing out on the starting lineup for the next match against Greece on Thursday is now a possibility with the player revealing his mental anguish before the Ivory Coast clash.
“I lost a battle with myself,” Kagawa told Kyodo News this week.
“There was pressure and nerves and at the start I made mistakes and I’m taking a good look at myself. I couldn’t get into a good rhythm and was beaten psychologically.
“We went into the match thinking we would be able to do well going forward, but both myself and the team were stiff and couldn’t move well.”
Kagawa was not the only one who struggled in a limp display by the Asian champions after they had taken the lead through a sumptuous strike by Honda in the 16th minute.
Japan coach Alberto Zaccheroni had called for his talented team to believe in themselves prior to the match, but their confidence shattered and the panic set in as they struggled to keep their powerful attacking opponents at bay.
The Italian coach is known for his loyalty and wholesale changes are unlikely, giving Kagawa another chance to rediscover the dazzling form that helped Borussia Dortmund clinch back-to-back Bundesliga titles.
That form, which also helped Japan clinch a record fourth Asian Cup in 2011, alerted Manchester United and he made the switch to Old Trafford in 2012 but the move has not worked out well.
After being shunted wide left by previous United manager Alex Ferguson and restricted in appearances, former Dortmund boss Juergen Klopp called for more love to be shown to the Japanese.
“Shinji Kagawa is one of the best players in the world and he now plays 20 minutes at Manchester United – on the left wing,” the German said last year.
“My heart breaks. Really, I have tears in my eyes. Central midfield is Shinji’s best role. He’s an offensive midfielder with one of the best noses for goal I ever saw.”
Life did not get any better under Ferguson’s successor David Moyes last season, with no goals in 18 league starts.
Moyes persisted with Kagawa wide when he did feature and Zaccheroni has been vocal in his preference for Honda, who also struggled badly after his goal against the Ivory Coast, to be his central creator.
Kagawa once bemoaned being forced wide for the Blue Samurai but his priority now is just being on the field to ensure his first World Cup extends to the knockout stages.
“We can’t let it end here,” he said.
“I still think we can play well and hopefully we can fix things. In order to win our second and third games we just have to continue believing in ourselves.”
(Writing by Patrick Johnston in Brasilia, editing by Ed Osmond)