Conor O'Shea identified Harlequins' April 11 showdown against Sale as the decisive fixture in their quest to finish in the top four of the Aviva Premiership.
A 23-9 victory over London Irish that saw Nick Evans, Sam Smith and Mike Brown score tries at Twickenham Stoop revived Quins' hopes of securing a place in the end-of-season play-offs.
Now six points adrift of fourth-placed Bath, O'Shea views the clash with Sale, who lie fifth, as pivotal.
"We know we have to win all four of our remaining games to be within a chance of finishing in the top four," director of rugby O'Shea said.
"We know that whoever wins when we go to Sale is in the fight for the top four. Whoever loses, isn't.
"It's going to be a real fight and I've always said it will be. We want to fight until the bitter end.
"Everybody plays each other and we have Leicester and Bath to come here.
"You have to keep going, take it day by day and not look too far ahead."
It took the vision of Danny Care to break Irish's stubborn resistance with the England scrum-half floating a 70th-minute pass to Smith for the wing to score.
"The standards we set ourselves are better than that," O'Shea said.
"We're never arrogant enough to take any Premiership win for granted, so we should be happy with the win, but our ambition and standards are higher.
"The breakdown was frustrating beyond comprehension throughout the game. We'll take the win, but we know there's more in this team."
Irish have little left to play for with Worcester destined for relegation and director of rugby Brian Smith admitted preparations have already begun for next season.
"We're in limbo now. We're looking up at the table thinking we can maybe catch the next team above us," Smith said.
"We can't do much more than that because there are only four fixtures left, so we're looking at the future.
"Obviously we want to win our home games and be competitive. Of course we want to win, but we also have one eye on next season.
"Giving game time to the younger blokes is part of the long-term plan."