The former quarterback coach was riding a bike in northern California when a car hit him almost a week ago.
READ MORE: NY Jets assistant coach dies after 'horrific' bike accident in California
On Thursday, his family announced his death. Now, people are remembering a man they called a coach, mentor, and a friend.
At 58 years old, Knapp is being remembered for the three decades he dedicated to coaching football.
He spent two seasons with the Texans and helped lead the team to win the AFC South championship in 2011.
Former quarterback Matt Schaub issued the following statement regarding Knapp's death:
"The impact you made was felt across the NFL by so many people. You were more than Coach, you were a friend, a confidant, a mentor. To say I was blessed to have you as my coach for 8 of my 17 years is an understatement. From drafting me in 2004 to ending my career with you in 2021, I am forever indebted to you for our time together. Your teachings, drill work, sarcasm, and enthusiasm will live on through all of us who had the honor to spend time with you. Our thoughts and prayers are with you and your family now and always. Love ya Knapper. RIP. Gone but never forgotten."
Former Texans quarterback TJ Yates also sent ABC13 a statement, referring to Knapp by his nickname.
"Knapper had an immediate impact on my life as soon as I entered the NFL. He was my coach that turned into my friend and mentor. He was instrumental in my success on the field, but his impact off the field was much more. Knapper was a special person who had an infectious attitude for life and was loved by everyone who he worked with. HE will be greatly missed by many. Our prayers are with his beautiful family and friends."
Sports analyst Spencer Tillman explained the significance of those statements.
"For TJ Yates to say what he said really says a lot, because he's not necessarily a top tier draft pick," said Tillman. "So, you want a guy that can work with you, that understands your skill set and has the patience enough to discover them and not necessarily shoehorn you into a system that they built their whole careers trying to establish. So, I think any good coach ... that's the mark of a good coach."
Tillman got to know Knapp during his time in Texas and then with the San Francisco 49ers.
He said aside from his coaching and mentoring, what stood out is his longevity on the sidelines.
"Our league is one that really doesn't suffer that 50 to 60-something crowd," said Tillman. "If you have not established yourself, you don't stay here 20 plus, nearly 30 years and not be efficient at what you do, and being really good at what you do. He was really good at what he did."
Those tributes from friends came along with final words from his family.
Part of the Knapp family's statement reads in part, "While his family, friends, and players still had so much to learn from him and desperately wished they had more time with him, God called an audible and wanted to go over the game plan directly with him. It will certainly be a masterpiece, just like Greg!"