By Peter Rutherford

OSAKA, Sept 28 (Reuters) – Tremendous in the second half against France, sensational in the first against Tonga, Argentina might just be contenders at this World Cup if they could only put a whole 80 minutes together.

One thing is for certain – they are leaving their coach Mario Ledesma as bemused as their opponents.

After trailing 20-3 at the break in their opener against France last week, the Pumas were on a mission to start well on Saturday against the Tongans in Pool C and they did not disappoint, scoring four tries inside the first half hour on the way to a 28-7 lead at halftime.

But a Tongan resurgence, coupled with the Pumas’ loss of focus, saw Mario Ledesma’s side fail to score for the rest of the game at the Hanazono Rugby Stadium, the only points of the second half coming courtesy of an unconverted try by the Pacific islanders.

Things could have been even worse for Argentina had referee Jaco Peyper taken a dimmer view of Tomas Lavanini’s reckless-looking, shoulder-high challenge on David Halaifonua as the Tongan powered toward the line in the last play of the first half.

Ledesma was at a loss to explain his side’s Jekyll-and-Hyde performances after the 28-12 win.

“My answer is the same as it was last week. If I knew the reason, this wouldn’t have happened again,” he told a media conference at the Hanazono Rugby Stadium.

“We made some substitutions (in the second half) and there were many chances that we couldn’t finish.

“We are in a vicious cycle.”

Defeat to France had left Argentina with an uphill task to avoid a pool-stage exit for the first time since 2003, and with group favourites England up next the only acceptable result for the Pumas on Saturday was a bonus-point win.

They secured that in a breathtaking display of forward play with hooker Julian Montoya scoring an early hat-trick of tries and winger Santiago Carreras grabbing the fourth with an intercept score.

“I think we were perfect in the first half,” added Ledesma.

“The maul was efficient and effective, and that was what we could not do in the previous match.”

Ledesma did not think his players had become complacent after they secured the bonus-point try but was concerned about the 29 tackles his team missed.

They will not be able to be so slack against England, he said, adding that Eddie Jones’s side would present an entirely different challenge in Tokyo in a week’s time.

“They look sharp, physically really sharp, and it’s a big challenge. Having a game against England to qualify for the quarter-finals, it doesn’t get any bigger.”

(Editing by Tony Lawrence)