The Houston Texans safety played with the wide receiver at the Baltimore Ravens, before both left the AFC North side during the off-season.
When asked who provided the greatest threat ahead of their game against the 49ers this weekend, the 35-year-old said: "Of course, Anquan. I played with Anquan. I know his heart. The guy's a beast when it comes to football. I played against him in college and played against him when I was in Baltimore and he was in Arizona.
"Now, that he's in San Fran, we've got this game. Anquan, [tight end] Vernon [Davis] and those running backs are really fast. They've got threats all over their offense, very explosive guys."
The Texans head to Candlestick Park following back-to-back defeats.