TOKYO, 29 Sep - After Ireland beat Scotland we wrote about how Irish line speed had dulled the attacking potency of Scottish fly-half Finn Russell. Line speed works because it forces the attacking team to make quick decisions and limits their attacking gameplan. If you want to spread the ball through multiple hands in an expansive attack, you need time. When the opposition charge out of their defensive line, however, they cut down that time.

Time is also the enemy of the defence. With limited time they must reorganise quickly. When they have to reorganise quickly the fast line speed has to go. You cannot organise quickly and also sprint off the defensive line. If you blitz from a disorganised defensive line it becomes very easy for the attack because the defence are no longer in a strong line.

The Japanese speed of attack in the victory over Ireland was ferocious. At every breakdown they wanted to get the ball back with minimal delay. Quickly recycling the ball led to Japan going forward and Ireland constantly going backwards. When you are spending your time running backwards just to get onside, line speed disappears.

Look at how Japan do not let the ball stay on the ground. They want to rush the defence as much as they can. If they can get tackled and play the ball in less than five seconds then that is advantage to the attack. You do not need huge ball-carriers to smash through defensive lines if you are running at retreating defenders. Rugby is a game for all sizes. Players are generally getting bigger but Japan have shown that speed is just as threatening as power.

Japan had more than 40 minutes' ball-in-play time against Russia, and achieved that again against Ireland. We are used to seeing Tier 2 nations tire during the second half. That fatigue is exacerbated by a high ball-in-play time. Lots of ball-in-play means lots of tackles and carries and other energy-sapping tasks. Given the speed at which Japan played, and the 176 tackles they had to make, they might have been expected to wilt. They did not. Ireland tired instead. If Japan can keep this up, in this heat and humidity, no team will beat them for fitness.

A word of warning, though. Japanese ball-carriers have improved because of the speed of recycling. They make yardage because opposing defences are not set. They will not look this good if they face a well-set defensive line. At that point the less powerful Japanese forwards will face more powerful opposition. They will be driven backwards and the opposition will be able to generate line speed to stop the wide attack.

For Japan to progress beyond the pool stage, and stand any chance in the quarter-finals, they need to produce that speed of play for 240 more minutes. Presuming that ball-in-play time averages 40 minutes per match, that is two hours. Two hours of the hardest exertion many of these players will have faced in their lives, in the extreme heat and humidity of Japan. Can they keep it up?

RNS sl/sdg/ns