Speaking after the Swans' 16-point loss to the second-placed Western Bulldogs in Canberra on Sunday, Roos said his side's lapse in the second quarter when the Dogs piled on eight goals to one cost it the game after it started the match in blazing fashion.
"To beat the quality sides you've got to play four quarters of quality football, you can't play three, so it was obviously the second quarter that got us in the end," he said.
"Games are now about intensity. You watch all games on the weekend and teams lift and drop, and the better teams, like Geelong, their intensity is very consistent throughout the game.
"Ours at the moment just wavers and goes up and goes down, and with a lot of teams we're seeing that happen.
"When that happened in the second, we weren't able to get back into the game during that period of time, and then in the other quarters, when we had the opportunity we did okay, and when they were going, we were able to control them a bit.
"But in the second quarter we just completely lost it in most facets of the game."
The Swans hold onto their fourth ladder position but are now even with the fifth-placed North Melbourne on points.
Roos said the equation is simple enough – win enough games and the Swans will remain in the top four. However, he said nothing will be gained from such a finish if the side can't play out a whole game.
"You've got to be realistic with where you're at. There's no point in stumbling into the top four; you want to win games of footy," he said.
"Unless we start winning, we're not going to finish there anyway.
"The good thing about today was that we found a couple of players, which was good, which adds a bit to your depth when you've got a lot of injuries, so that will take care of itself if we win enough games."
He refused to blame injuries to Leo Barry, Michael O'Loughlin, Adam Goodes and Nick Malceski for the Swans' slump, but said it had contributed.
"It hurts because better players are better players, but that's just the reality of where you're at," he said.
"But you can't worry about who's not there; you can just prepare the team that's there. From a positive point of view, it was good to get some young guys in and they contributed well."
Roos said Malceski and Barry are chances to return next week against Fremantle, while Goodes "should play" in the Saturday night match.
