The 19-year-old midfielder was making his O's debut on loan from QPR but lasted just 38 minutes of the FA Cup win over Southport before rupturing his anterior cruciate ligament.
Sutherland now faces up to nine months on the sidelines and Slade told the club website: "Myself, the staff and the players are all devastated at the news.
"In the short time he was here, Frankie gave a great example of how a young pro should carry themselves with his dedication and commitment to the cause.
"Everybody was wishing him to do well on his debut and he started so brightly. Frankie is made of the right stuff and has a great attitude. I'm sure he will bounce back fitter and stronger than before."
Sutherland, now beginning his rehab back at Loftus Road, had a message for his Orient team-mates.
He wrote on Twitter: "Just want to say thank you to everyone at Leyton Orient especially all the lads. Great bunch and hope they can get promotion!"