Meriweather also said, after another heavy fine, that it might be time to change the way he tackles.
Lacy exited the game with a concussion; Meriweather left later in the game with a concussion after a hit on running back James Starks.
This is not the first time Meriweather has been fined. In 2010, he received a $50,000 fine for two helmet-to-helmet hits with New England. The following season with Chicago he was fined a combined $45,000 for hits in back-to-back games.
Meriweather played just half a game with Washington last season. It could be time for him to alter the way he tackles.
"Everybody has to change the way they tackle," Meriweather said. "They say hit low. I see people get concussions from hitting too low too. There's no real safe way to play this game. You know what you signed up for, and if you're gonna do it, you do it 100 percent."
The Redskins' coaches had no issue with the hit Meriweather made on Starks that knocked himself out. He's questionable for Sunday's game against the Detroit Lions.
"I feel good right now," he said. "It's all up to the doctors. I have no control over it."
Meriweather received his fine for the first-quarter hit on Lacy. It was Meriweather's first game since Nov. 18 because of a torn ACL.
The Redskins like the energy he adds to the secondary, but they also need him on the field.
"I kind of figured that it was my first game back," Meriweather said. "I was overaggressive. I can't say overaggressive; that's the way you want to play the game is aggressive. ... I let my coaches evaluate it, and I'll do what my coaches say."
What he won't do is think too much on the field about whether a hit he's about to make will draw a fine.
"To be honest, I try not to think when I'm playing," he said. "Whatever comes on comes on. The people who think while they're playing are the people who retire early."
Meriweather wasn't the only Redskins player fined. Center Will Montgomery received a $10,000 fine for an illegal peel-back block, and long snapper Nick Sundberg received a $7,875 fine for unnecessary roughness.