The Grizzlies intend to keep Barnes, sources said. Only $1 million of Barnes' $3.5 million salary is guaranteed if he's waived before Wednesday, but Memphis wants Barnes for perimeter depth.
Ridnour didn't stay in Charlotte long, as the Hornets traded him and a conditional 2016 second-round draft pick Thursday to the Thunder for guard Jeremy Lamb. That deal comes just a day after Ridnour was traded by the Orlando Magic to the Grizzlies.
The Hornets have been busy this offseason.
Barnes, 35, is in the final year of his contract. He averaged 10.1 points, 4.0 rebounds and 1.1 assists while starting 74 games for the Clippers in 2014-15.
Barnes, however, wore out his welcome in Los Angeles, as his on-court temper and penchant for getting fined constantly irked head coach and president of basketball operations Doc Rivers, who had been looking to deal him for about two years.
The 34-year-old Ridnour averaged 4.0 points and 2.0 assists while playing 47 games for the Magic last season. He has career averages of 9.3 points, 4.5 assists and 2.3 rebounds per game.
The 14th overall pick in the 2003 draft, Ridnour is joining his seventh NBA team. He now has been traded six times in his career.
Ridnour was drafted by the SuperSonics in 2003 and is the first Sonics player to return to the Thunder since they moved from Seattle to Oklahoma City in 2008, according to ESPN Stats & Information.
Lamb, the 12th overall pick in the 2012 draft, will rejoin former UConn teammate Kemba Walker in Charlotte's backcourt. They were the two leading scorers in the Huskies' 2010-11 national championship run.
In 148 games over three seasons with the Thunder, Lamb averaged 7.0 points, 2.1 rebounds and 1.1 assists in 15.7 minutes.
"Jeremy Lamb is a quality young wing player who we believe has the talent to help our team," Hornets general manager Rich Cho said in a statement. "We look forward to adding him to our rotation next season."