GLENDALE Ariz. -- The Cardinals defense suffered a major blow Monday when defensive tackle Darnell Dockett sustained a torn ACL in his right knee midway through training camp practice at University of Phoenix Stadium.
''Thank you all for your support and get well wishes. I really do appreciate it,'' he said in a tweet Monday night. ''This will be a tough road to recovery but I been through worse.''
After lying on the ground for a few minutes, holding the knee while rocking and back and forth in some pain, Dockett was carted off the field. The Cardinals later confirmed an ACL tear, after an MRI exam.
"I don't know what happened. It's just part of football. His foot got caught in the ground," said nose tackle Dan Williams, describing the 11-on-11 play on which Dockett was hurt as routine. "It's the chance that we take when we play this sport. You hate to see a guy go down."
Veteran Frostee Rucker and 2014 fifth-round pick Ed Stinson both ran reps with the first team after Dockett went down, but Rucker will likely be the replacement and played well in relief of Dockett last season. Fourth-round pick Kareem Martin will also be asked to step up and take some reps in sub-packages.
Losing Dockett, a three-time Pro Bowler, is a major blow to a defense that also lost linebacker Karlos Dansby to free agency and linebacker Daryl Washington to a year-long suspension for violating the league's policy on substance abuse.
Free safety Tyrann Mathieu will give the team a boost when he comes off the PUP (physically unable to perform) list Tuesday and begins practicing Wednesday.
''Praying for my brother,'' tweeted Mathieu, who tore his ACL and LCL on Dec. 8.
I literally been sick to my stomach for the past couple hours thinking about @ddockett one of my closest friends. Speedy recovery my friend
— Adrian Wilson (@adrian_wilson24) August 19, 2014
New York Giants safety Antrel Rolle tweeted ''everyone plz say a prayer for one of my best friends and wish strength and a speedy recovery plz. No injury will keep him down.''
"He's a great player; one we count on to be a leader," defensive end Calais Campbell said after Monday's practice. "He was on the ground for a while. I came over and told him to stay strong."
Dockett, Campbell and nose tackle Dan Williams formed a formidable defensive front that helped the Cardinals rank first against the run.
Dockett is a three-time Pro Bowl selection and four-time team captain.
''I played against him for three of those years when I was in Seattle,'' Cardinals tight end John Carlson said. ''He's a beast.''
Dockett has spent his entire career with Arizona. He and Larry Fitzgerald are the longest-tenured players on the squad. Both were drafted by the Cardinals in 2004 -- Fitzgerald in the first round out of Pittsburgh, Dockett in the third round out of Florida State.
Dockett played in his first 104 games before a shoulder sidelined him for one contest in 2010. He missed another game in 2012 with a hamstring injury.
The vocal, emotional Dockett had talked about the optimism of the coming season, saying that anything short of the playoffs would be a big disappointment. The Cardinals were 10-6 last year, in Bruce Arians' first season as head coach, but failed to make the playoffs.
The injury will further test the skills of defensive coordinator Todd Bowles.
Rucker, an eight-year NFL veteran, appeared in all 16 games for Arizona last season, one as a starter. He started all 16 games for Cleveland in 2012.
The Associated Press contributed to this report.
