The Samurai Blue got a reality check Wednesday when a lowly-rated Turkmenistan team pushed them harder than expected in the teams' Asian Cup group stage opener in the United Arab Emirates.

Japan's narrow 3-2 victory over the Group F underdogs, spearheaded by a go-ahead brace from Yuya Osako, left the four-time Asian Cup champions recalibrating their expectations.

"I didn't think it would be so tough," said midfielder Genki Haraguchi, who helped set up two of Japan's goals.

(Yuya Osako (15) equalizes for Japan with the first of his brace)

In the first half at Abu Dhabi's Al Nahyan Stadium, Japan focused their attacking forays down the center, with Haraguchi and his teammates confident the "good form shown in training" would translate to the pitch on match day.

But, in the face of Turkmenistan's resolute focus, Japan were unable to break through the defense and conceded the first goal of the match on Arslanmurat Amanov's stunning long-range blast in the 26th minute.

Japan Manager Hajime Moriyasu switched tactics in the second half, shifting the attack wider in hopes of finding a leveler. Working in from the left in the 56th, Haraguchi picked out Osako from a crowd in the box and the forward showed lovely footwork to put the ball onto his right and strike true.

Four minutes later, Haraguchi headed in a ball from the left, and Yuto Nagatomo took advantage of some half-hearted defense to lift the ball over Turkmenistan goalkeeper Mammet Orazmuhammedow, allowing Osako to tap in for a 2-1 Japan lead.

(Ristu Doan (21) scores what turns out to be the winner with Japan's third goal)

With rising star playmaker Shoya Nakajima unavailable for the tournament due to a calf injury, Moriyasu started Haraguchi in an attacking trio behind Osako and alongside newcomers Takumi Minamino and Ritsu Doan, who added the third and eventually winning goal with his left foot in the 71st minute.

"We have to win in Asia," the 27-year-old midfielder said, adding the victory would help wipe away the frustration of getting knocked out in the round of 16 at last year's World Cup in Russia.

Japan, aiming for an unprecedented fifth Asian Cup trophy, play their second Group F match on Sunday against Oman, who opened with a 2-1 loss against Uzbekistan, Japan's opponents in their final group-stage fixture next Thursday.