Slauson plans to appeal the fine, a source told ESPN NFL Insider Adam Schefter.
Cushing tore his left anterior cruciate ligament in the second quarter of the Texans' 23-17 win Monday night on a low, rolling hit by Slauson. He walked off the field on his own, but didn't return to the game. He was placed on injured reserve Wednesday.
"I thought it was unnecessary," Texans defensive coordinator Wade Phillips said earlier Thursday. "Whether it was legal or not, all that stuff -- I think it's just unnecessary to hit a defensive player when he can't see you."
Slauson was not penalized on the play. Phillips said if he'd hit Cushing in his head, he would've drawn a flag.
"If a guy's coming in front of me and cuts me, he can see that and yeah, they can get away with that," Phillips said. "But when they don't see you, I think the league needs to look at something like that."
Slauson said Wednesday he felt like it was a "clean block" and was not trying to hurt Cushing. Jets coach Rex Ryan defended Slauson on Thursday, and called the block and the resulting injury to Cushing "unfortunate."
"I heard that the league is looking into that," Ryan said. "My take when I saw it, and now I've seen TV copies and all that, is that obviously, it's an unfortunate thing. We talked about that."
"I know the intent of Matt Slauson was not to injure Brian Cushing, without question," Ryan said. "We wouldn't try to injure anybody, but a great player like Brian, it's really an unfortunate thing. It's obviously in their (the league's) hands, but I know the intent of our player, though."
Houston left tackle Duane Brown said Thursday "it's a very fine line, when you're talking about cut-blocking." The team's offensive linemen are coached to do it, and also on when to hold off to avoid hurting a defensive player.
"The way we cut, it's always going upfield," Brown said. "The way he (Cushing) got cut, the guy (Slauson) was actually coming back towards the play. He was facing the running back, coming back toward the line of scrimmage, which I don't think is legal. We don't coach that at all. We don't go out and execute that kind of cut block."
Brown said cut-blocking is "encouraged" in Houston's offensive scheme, but he added, "You have to be careful."
Phillips praised the league's efforts to monitor illegal hits.
"I think the league is trying to do all the right things, they always have," Phillips said. "When these cases come up, they look at them. I think the league will look at it."
Information from ESPNNewYork.com's Rich Cimini, ESPNNewYork.com's Jane McManus, ESPN NFL Insider Adam Schefter and The Associated Press was used in this report.