With two league games to go, Harlequins are one point and one place above the Sharks in the race for fourth place and the upcoming clash is as close to a season decider as both teams will get.
Jones said: "We did not turn up against Bath - it is as simple as that.
"We were second best in all departments, we did not get across the gain line enough, and we could not dictate play.
"I am expecting the lads to be hurting massively after that and I am wanting a massive improvement against Harlequins or our season is as good as over. It is that big a game.
"Quins will be as tough a challenge as any, especially away from home when we will be up against a party style atmosphere.
"But we are confident we can beat them - we would of course have preferred it to have been as Edgeley Park but that is sport for you.
"We need to try and dominate their forwards, get some attacking ball and defend well.
"It has to better than against Bath or we will certaintly not win."