Leach's comment regarding his former teammate came in reply to a tweet by NFL Network's Ian Rapoport, but Leach later deleted his tweet, according to Michael McClymont of The Score.
In 2010, Cushing was suspended four games for violating the league's policy on performance-enhancing substances on the heels of a fantastic rookie campaign that saw him win Defensive Rookie of the Year honors.
Leach was Cushing's teammate in 2009 and 2010 before joining the Baltimore Ravens for the 2011 season.
The 35-year-old last played in 2013 and finished his career as a three-time Pro Bowler and three-time All-Pro First Team selection.
Cushing hasn't made a Pro Bowl since his rookie year, and he has appeared in all 16 games just once since doing so during the 2011 campaign.
With Cushing out of the mix at inside linebacker, Houston's depth will be tested over the next two-and-a-half months.
Benardrick McKinney will continue to hold down one spot, while rookie second-round pick Zach Cunningham and undrafted rookie Dylan Cole will vie for playing time alongside him.