The England flanker played one season for Tokyo-based club Ricoh Black Rams in 2011 as part of a globetrotting spell which also included stints at the Highlanders in New Zealand and French Top 14 side Stade Francais.
"This win will have been massive for the game in Japan. I was surprised at how big rugby was there anyway," Haskell said.
"They like soccer and baseball was huge too, but rugby was also popular. The university games get 60,000-odd who come to watch.
"The league had viewers but not to the same extent, but university rugby was already there and with the next World Cup being hosted by Japan, it might be a catalyst to kick things forward.
"Maybe it will convert that guy who would go for baseball into rugby because they are mad for it over there.
"When I went to Japan, I found a very disciplined, skilful set-up, especially with their tackling - they weren't scared of anyone.
"Training was often long and if you could try to have refined that down and distill it into what we saw at the weekend, then a lot of those teams would be a lot more competitive.
"The problem is that there is a lot of cultural stuff over there that makes a big difference.
"If you have got a hierarchy of players - at Ricoh we had 63 players in the squad - when you went to a scrummage session if you are playing eight, there were six sets of front rows to go through."