Tries from Tom Brady and Dan Braid took Sale into a 12-7 half-time lead, with Christian Wade responding for the visitors. And although Wade's second score and 10 points from the boot of Tommy Bell gave Wasps a 20-18 advantage with eight minutes to go, Nick Macleod's late penalty secured the win for the Sharks.
"We didn't play well second half. We got the ascendancy in the first half and they did well from a couple of breakaway tries," Diamond said. "I thought we lost our composure in the second half but again it's difficult. We'd had a lot of ball in the first period and just couldn't convert those drives in the last minute."
He added: "We didn't play very well to be honest so it was a bit quiet in the dressing room. I don't think we were helped by the referee, there was a lack of communication from his touch judges and they were able to spoil a lot of our driving play."
After a disastrous first half of the campaign, which saw the Sharks bottom, they have improved since Christmas securing six wins in the final 11 games to finish 10th in the league.
But Diamond insists there is no excuses should they underachieve again next season.
"We've had a poor season considering what our expectations were and are with a facility like this (the Salford City Stadium)," he added.
Wasps' director of rugby Dai Young allayed fears over lock Joe Launchbury who has struggled with a slight injury since England's defeat to Wales in the Six Nations.
Young said: "He's had a hell of a season and you've got a kid there that goes above and beyond the call of duty on occasions. He's gone out there and put his body on the line for big periods, he's got a bit of a stiff neck and a sore shoulder.
"He's at no risk of an operation or being out for any length of time. He is a little bit battered and bruised at the minute and he probably deserves a rest. I'm sure that he'll be ready to go to Argentina with England if required."
- Sports & Recreation
- Christian Wade
- Nick Macleod