The host nation crashed over for a stoppage-time try in a 38-19 win after Samoa were punished for a squint scrum feed on their own five-metre line.

Japan meet the Scots in the hosts' final pool match on Sunday.

"I've never seen a crooked feed [penalised], certainly at the World Cup or in the Six Nations," said Townsend.

"I think it's an incredible call to be honest. It's something that has not been refereed and there's been an agreement that there is more latitude for scrum-halves putting the ball in because you are the team that's won the scrum.

"To see it in a World Cup really surprised me. To see it as we went into injury time for a game-changing decision was an even bigger surprise."

Scotland must secure a bonus-point victory over Russia on Wednesday to close the gap on Japan to four points going into Sunday's meeting in Yokohama.

Townsend's side would then need to prevail against the hosts to reach the quarter-finals but could miss out with a win if Japan picked up a losing bonus point.

Townsend has made 14 changes to his starting line-up for the match with Russia, keeping key players fresh for the weekend.

Star men such as Finn Russell and Stuart Hogg are left out completely, with Blair Kinghorn, Pete Horne, Ben Toolis and George Turner making their first appearances in the tournament.

"We have had a long rest into this game," said Townsend. "Obviously, we don't have too much of a rest into our final game.

"A three-day gap between games is the shortest you can get. What we can do with the players on Thursday depends on what happens in Wednesday's game.

"We've obviously got Japan on the back of our minds but the front of our minds is all about Russia and delivering a winning performance and getting a bonus point. It's important we build on the momentum that we created against Samoa.

"Russia have gained in confidence. They look a fit team. They've been better in the second half in their last two games. Their defence has certainly improved. They had 90% tackle completion against Ireland. They have some physical players, who are good rugby players too. They have a solid scrum, one of the best you'll see.

"It's their last game, so they will throw everything into this. We're expecting as good a performance as they gave against Ireland, maybe another level up."