Sheffield United manager Bryan Robson conceded tonight's impressive second-half display in a 3-1 Carling Cup win over Chesterfield was tempered by an injury to new captain Gary Naysmith.

Summer signing Naysmith, who arrived from Everton as part of the deal that saw Phil Jagielka move to Goodison Park, was forced out of the action early in the game with knee ligament damage.

Two first-half goals from Blades striker Jon Stead and a third from Danny Webber not long into the second period eased United to victory - but progression through to the second round came at a price.

Robson said: "The only things about this competition which is a concern to you as a manager are like Gary Naysmith doing his knee ligaments.

"I hope it's not too serious - but it makes him a doubt for the weekend.

"It will have to settle down before we get a diagnosis, but it's a sore one."

On his side's display, Robson added: "There were a lot of things we weren't particularly good at in the first half - especially the direct ball, which caused us too many problems - and we didn't pass the ball as well as we'd have liked.

"But Jonathan Stead's was a cracking goal, so that's good for his confidence, and in the second half we played how I'd expect us to play.

"We defended better, and the actual passing and movement off the ball was very good in the second half - so I was pleased with the improvement."

Chesterfield manager Lee Richardson was pleased with his side's overall showing.

He said: "I genuinely thought we did play well.

"We lost goals at crucial times, which is always going to make it very difficult against a team that's got a bit more strength in depth.

"We've seen Sheffield United's quality and ruthlessness, punishing us - almost the first shot at goal ends in the back of our net.

"The goals were the types of situation you don't tend to get punished for at our level, but these lads have cost a couple of bob."