The race for sixth place in the Aviva Premiership and a guaranteed spot in the top tier of European rugby saw Harlequins pull a point further clear of Sale on Saturday after they got a try bonus point at home to Newcastle.
Sale, in seventh, beat bottom side London Irish 30-15 at the Madejski Stadium but were only able to score three tries, through Mike Haley, Danny Cipriani and TJ Ioane.
Diamond conceded his side were not at their best but was pleased with their second-half performance as they claimed their first win at Irish in a decade.
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The Sharks director of rugby said: "We didn't play that well in areas. We made basic errors and we controlled possession in the first half just enough.
"We turned around just in front and then we played well in the second half."
Sale now face a run of European and domestic fixtures in quick succession that could define their season, and Diamond has no intention of resting any of his key men.
He said: "We play Montpellier on Friday, then we travel to Bath to play them on the Wednesday and then we have to play them (Bath) on Sunday. We will be going full strength. "
Diamond also sympathised with the plight London Irish have found themselves in as they trail second-bottom Newcastle by four points, with the two teams meeting at Kingston Park on April 17.
The Exiles got themselves back to within a point of Sale at 16-15 in the second half, Johnny Williams going over to add to Sean Maitland's first-half try, but two late Sharks scores saw the visitors run away with the match.
Diamond said: "Anyone can be where London Irish are. They can count on their fingers how many games they could have won this year. It's a tough league. It is just that consistency you need.
"I have played against London Irish for 30-odd years and somebody has to go down, that is the beauty of the league. The competition is so strong that the Aviva Premiership is pushing itself forward.
"It is easy saying it when you are not involved but I have been involved in a dogfight three years ago and London Irish are still not out of the woods. They have Newcastle in two weeks but we have to take the emotion away from it. We want to be in the top six and reach as high as we can."
Irish head coach Tom Coventry felt his side could have had two further scores against Sale which were ruled out but admitted their trip to Kingston Park on Sunday week is a real make-or-break.
Coventry said: "It was a pretty big disappointment today after we worked to get ourselves into the game. There were a couple of big moments.
"I am concerned about a couple of opportunities that were missed by the officials today which led to putting us under the cosh. There were a couple of big moments that swung the game.
"We can dwell on this as long as we like but we have to get back on the horse and see if we can get some footy under our belt that is good enough to win at Newcastle."
London Irish all but relegated from Premiership after Harlequins defeat
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London Irish all but relegated from Premiership after Harlequins defeat
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