The Urawa Reds edged Sanfrecce Hiroshima 1-0 at home Saturday to surge ahead in the J-League under the scrutiny of new Japan manager Javier Aguirre.
Sagan Tosu, who started the day tied on points with leaders Urawa, lost 2-0 at home to FC Tokyo and slipped to third spot on the table. Kawasaki Frontale climbed to second after outlasting Cerezo Osaka 5-4, also at home.
Urawa stood top of the board with 40 points from 20 games, one point ahead of Kawasaki, with Sagan two points further back.
Mexican Aguirre, a former Espanyol coach, was watching a J-League match for the first time since he replaced Italian Alberto Zaccheroni as Japan's coach after the Blue Samurais' winless exit from the World Cup in Brazil.
Urawa captain Yuki Abe scored the lone goal at 22 seconds.
"The match was well disciplined for 90 minutes. I took note of a number of players," the 55-year-old manager told reporters.
He is expected to announce his squad later this month for a friendly against Uruguay at home on September 5, his first game in charge of Japan, and another against Venezuela four days later.
"I want to select players who can fight on for 90 minutes both on offence and defence," said Aguirre, who piloted Mexico to the last-16 round at the World Cup in 2002 and 2010.
Of the Reds and Sanfrecce players, only Urawa goalkeeper Shusaku Nishikawa and Hiroshima midfielder Toshihiro Aoyama made the World Cup in Brazil.