Charlton star Mark Marshall will be on the sidelines for a long time, says Addicks boss Karl Robinson.

Marshall, 30, injured his knee in Charlton’s pre-season win over Stevenage on Saturday.

The Bradford summer signing left the ground in a knee brace on crutches.

Robinson said: “We’re playing well, but we had a really bad injury on the weekend.

“It’s not good. It’ll be a long one and we’re disappointed about it.

“It happened when he went in for a tackle, it wasn’t the opponent’s fault.”

Marshall, who was one of Charlton’s most exciting summer signings, arrived to high expectations from Addicks fans.

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But his injury will come as a massive blow for the club, who might have to bring in another winger before the transfer window shuts.

Robinson is pleased with his team’s progression in pre-season – but sent a clear message to the Charlton hierarchy.

Speaking on talkSPORT’s kick off show, he added: “My players have been brilliant this summer. We’ve had a number of games in Ireland and England.

“We’re looking fitter and getting better. Hopefully the board are listening, we still need four more players.

“We’ve not got long to go but we still need three or four players in key positions. We’re planning for a very exciting season.

“Our fans have been through turbulence for whatever reasons, but all I care about is making them proud on the pitch.”