Charlton have made their first summer signings by bringing in midfielder Alan McCormack and defender Gary Doherty.
But, as the pair arrived at The Valley, right-back Frazer Richardson moved to Southampton in a £450,000 deal.
The 26-year-old McCormack arrives as a free agent after leaving Southend by mutual consent after four seasons.
Charlton manager Phil Parkinson said: "I'm really pleased to have Alan on board.
"The thing that struck me about him more than anything else was his hunger. Anyone I bring into this club this summer, whether it's a member of staff or a player, has got to relish the challenge, as I am doing, because it's going to be a challenge this season.”
Doherty (pictured), who was out-of-contract, won the League 1 title with Norwich City last season and has signed a two-year deal.
Parkinson said: "He's an experienced centre-back with great quality and I'm delighted he's agreed to join us.
"Of all the centre-backs out there in the summer he was the one I targeted. It's taken a while to do the deal for various reasons.
"From day one, Gary expressed his interest in coming to Charlton. He wants to be a part of what we hope is going to be a successful season."
Richardson links up with former Addicks boss Alan Pardew having made 40 appearances in his one season at the club.