GLENDALE, Ariz. (AP) -- On the day the Arizona Cardinals went back to work for the first time since Darnell Dockett went down with a knee injury, the impact of losing the big defensive tackle for the season was softened a bit by the return of safety Tyrann Mathieu and nose tackle Alameda Ta'amu.
The 'Honey Badger' Mathieu, a crucial component of Arizona's talented secondary, went down in the 13th game of his impressive rookie season a year ago with a torn ACL and LCL. The massive Ta'amu tore an ACL in the season finale at San Francisco.
With just Frostee Rucker and two rookies at Dockett's position, the Cardinals signed two free agent defensive linemen on Wednesday - 6-foot-2, 330-pound Isaac Sopoaga and 6-6, 305-pound Ryan McBean.
Sopoaga is a 10-year NFL veteran who split last season with Philadelphia and New England. McBean has been out of football for two years. He played in 48 NFL games, all but one of them with Denver.
The first-string job is going to Rucker, who has played in all 16 games the last three seasons, including 16 as a starter for Cleveland in 2012.
''I've been preparing myself since last year, anytime I'm out here, to be the guy,'' Rucker said after Wednesday's practice, ''because I've been in this league long enough and I know injuries happen and things happen and you've got to prepare yourself and be ready. ... I don't think there's going to be any drop-off. I've just got to make sure and prepare myself to fall in the footsteps of No. 90 (Dockett).''
Dockett, who missed just two games in his 10 NFL seasons, will undergo surgery soon, coach Bruce Arians said.
''He's obviously done for the season but I plan on having him on the sidelines with us all year long because of his spirit and leadership,'' the coach said. ''It's something we need and don't want to lose.''
Dockett was hurt Monday in an 11-on-11 drill.
Replacing his impassioned on-field leadership will be a challenge.
''I've just got to be more of an emotional leader, more vocal, just making sure that I don't let the team take plays off,'' defensive end Calais Campbell said. ''That was the stuff Dockett was real good at. If we are messing up practice, he'd call timeout and get the whole defense together, and make sure we got it together.''
The loss of Dockett further depletes the middle of an Arizona defense that ranked sixth overall and first against the run in the NFL last season.
''You lost three critical pieces - Karlos (Dansby) and Daryl (Washington) and now Dockett,'' Mathieu said. ''That pass rush might not be there this year. We may have to cover a bit longer. That's why Patrick (Peterson) gets paid, that's why we brought in (Antonio) Cromartie, and that's why I've got to step up.''
With almost three weeks to go, chances are better than had been expected that Mathieu and Ta'amu will be playing in the season opener against San Diego on Sept. 8, a Monday night game.
Mathieu's versatility and playmaking ability will be put to use the minute he appears ready for it.
Arians calls Mathieu ''a game-changer'' with his ability to tip balls, knock balls loose or intercept them. Versatility adds to his value.
''You don't have to substitute because he has corner ability. He's a safety that can cover, he can play in the slot, he can go out wide,'' Arians said. ''You can stay in your base package and really you still have three corners out there and also great range in the deep end of the field. He allows us to do a lot of different things.''
Mathieu and Ta'amu will work out individually for a day or two before being eased into practice with the rest of the team.
But, Mathieu said, ''I'm just waiting for that moment where I really get tested, then I'll know for sure whether I'm the same player or whether I have to pick it up a little.''
Dockett's entire 10-year NFL career has been with Arizona, but there's a good chance he has played his last game as a Cardinal.
Next year is the last year on his contract and Dockett, who will be 34 by then, will be scheduled to make $6.8 million with a $9.5 million cap hit - a price the Cardinals might not want to pay.
NOTES: Starting C Lyle Sendlein practiced after missing three weeks with a calf injury. ... G Jonathan Cooper (toe) and MLB Kevin Minter (pectoral muscle) remained sidelined.
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