McKenzie played for the Saints in 2008 but suffered a fractured right kneecap in November that sidelined him the rest of the season. Prior to that, McKenzie started 62 of 63 games, with 225 tackles, 58 passes defensed, 12 interceptions and one forced fumble.
Some believed it might be a career-ending injury, but McKenzie apparently has regained his speed and is ready to play.
He worked out during the summer for Seattle, and now will have to learn a new defensive scheme in New Orleans, where he played from 2005 to 2008.
The unbeaten Saints will need all of the help they can get in preparation for next Monday night's game against New England. They have been short on cornerbacks because of injuries to Tracy Porter, Jabari Greer, Randall Gay and Leigh Torrence.
The Saints placed Torrence on injured reserve late Monday with a shoulder injury.
Fortunately, the Saints are expecting positive news regarding their other players with injuries.
Running back Reggie Bush (knee), defensive tackle Sedrick Ellis (knee) and cornerback Jabari Greer (groin) -- none of whom played Sunday against Tampa Bay --- all are expected to play against the Patriots.
Adam Schefter is ESPN's NFL Insider. Information from The Associated Press was used in this report.