Takeshi Okada's boast that his country would reach the semi-finals of South Africa 2010 certainly appears far-fetched but at least Keisuke Honda's goal eased the pressure on the Japan coach.
Honda revved up Japan's bid to reach the knockout phase with the only goal to condemn Cameroon to their first-ever opening game defeat in the competition.
Okada has come under fierce criticism in his own country after a string of dreadful performances leading up to the tournament but this deserved victory will have earned him some respite.
And it will be Cameroon's coach Paul Le Guen who is certain to be more severely scrutinised, after his bizarre game-plan that included playing star man Samuel Eto'o on the right side of midfield.
Eto'o was thoroughly ineffectual and did little to prove Cameroon legend Roger Milla wrong.
Milla, who played a key role in Cameroon's historic run to the 1990 quarter-finals, had publicly questioned the Inter Milan forward's commitment to his country and there was nothing in this performance to dispel that theory.
Both nations went into the game in atrocious form and it showed in a dreadful first half almost entirely devoid of incident. With Japan opting for an ultra-defensive approach, and Cameroon unable to break them down, it was not until the 38th minute that a goalkeeper was tested.
Eiji Kawashima easily dealt with Eyong Enoh's drive but, out of nowhere, Japan capitalised on a trademark Cameroon defensive lapse to take the lead against the run of play.
The impressive Daisuke Matsui's cross found Honda unmarked and he cleverly found the corner from close range.
Cameroon displayed a little more urgency in the second period but Eto'o, in particular, had the air of a man bewildered. Le Guen made a raft of substitutions as time ebbed away and defender Stephane Mbia struck the crossbar with a wonderful shot from distance but Japan clung on to ensure their opponents have now gone eight games without a win.
Okada will face a more severe test against the Netherlands this weekend but for Le Guen, it is certain to be a difficult week of reflection as he bids to rescue his campaign.
JAPAN (4-1-4-1): Eiji Kawashima; Komano, Tanaka, Nakazawa, Nagatomo; Abe; Endo, Hasebe, Matsui (Okazaki 69 ), Honda; Okubo (Kisho Yano 82).Subs (not used): Narazaki, Kawaguchi, Uchida, Daiki Iwamasa, Konno, Nakamura, Nakamura, Inamoto, Tamada, Morimoto.
CAMEROON (4-3-1-2): Hamidou; Mbia, Bassong, Nkoulou, Assou-Ekoto; Makoun (Geremi 75), Etoundi, Matip (Emana 63); Eto'o; Choupo-Moting (Idrissou 75), Webo.Subs (not used): Kameni, Ndy Assembe, Song, Song Billong, Gaetan Bong, N'Guemo, Emana, Chedjou Fongang, Mandjeck, Vincent Aboubakar.