Lewis, 22, said the Hawks were "not ready to play" before the 29-point loss to the Tigers, and will learn from their mistakes with two home-and-away matches to come before September action kicks off.
"We've played some big games this year, and at the moment, we're so far behind what we expect of ourselves and the way we normally play," he told hawthornfc.com.au after the game at the MCG.
"We've just got to come with a mindset that it's just another final, and today we just didn't come with that mindset.
"I don't think it's hard for us to find motivation, but it's hard being at the top of the ladder when you've got sides wanting to make the eight when their backs are against the wall and they'll do anything to win.
"If you're not on your game like we weren't today, you see what happens."
The Hawks have the luxury of knowing they'll finish top three, and will play the Western Bulldogs in the first week of the finals.
However, Lewis said there are still tough assignments to come for his side given the number of opponents fighting for their lives in the 2008 season.
"It's like North Melbourne six weeks ago when their backs were against the wall and they upset us again," he said.
"If we put out performances like that in the finals, we're not going to get anywhere near them."
Lewis said the players "haven't spoken" about directing the ball to Buddy Franklin more than usual, despite the fact the spearhead is on the verge of becoming the first player since Fraser Gehrig in 2004 to kick 100 goals in a season.
"We've got a forward structure and we know where to kick it and if Buddy is in the right spot, we kick it to him," he said.
"If Roughy's [Jarryd Roughead] is in the right spot, we kick it to him.
"Whether he kicks 100 or not, it's not on our minds. He might have done it today if he could have kicked straight.
"When we take the ball forward and we see a big 6ft 5 guy presenting at us with his arms wide, you can barley miss him. You've just got to kick the ball to him if he's leading with intensity.
"We've just got to get the ball to other forwards as well. Sometimes we do become a bit too Buddy-focused, but it's not because of the 100 goals; it's just because he's a big, fast forward.
"But, I think him getting 100 goals will be a great thing for the game, and hopefully he gets it."
