Harlequins secured their place in the English Premiership play-offs on Saturday, but lineout coach Jerry Flannery says they must either tighten up or forget about being crowned champions for the first time since 2012.
Harlequins' thrilling 44-33 victory over Bath saw them take the fourth and final play-off spot with two games of the regular season remaining.
It is the first time in seven years they have made the play-offs.
They join defending champions Exeter and Sale, the latter sealing their place in the play-offs with an impressive 22-12 win over already qualified Bristol on Friday.
Bath's fourth successive defeat leaves them battling to make the top eight, which would qualify them for next season's European Champions Cup.
Harlequins were certainly value for money in touching down six times, including one by veteran scrum-half Danny Care.
Former Munster and Ireland hooker Flannery was pleased to have a play-off place assured but he did not enjoy watching the spectacle.
"I'm delighted that we got the result and secured top four, but it was hard work doing it," said Flannery.
"I can't say it was overly enjoyable for me and although I'm sure supporters and neutrals loved it, I found it pretty stressful."
"There are areas of the game that we have to sharpen up if we want to push on when we get into the semis."
The 42-year-old Irishman conceded Harlequins traditionally play attacking, crowd-pleasing rugby, but he pleaded also for some common sense to be displayed when it came to defending.
"I have to accept that Harlequins play rugby a little bit differently to what I'm used to," he said.
"It's unconventional and I haven't been involved in a team that plays the way Harlequins do before.
"It's not that you let your standards slip, but there has to be a bit of give and take because the DNA of this club is attack.
"But we will not win the league if we don't tighten up in defence."
Sale's seventh straight Premiership win, a new club record, means they will be in the end-of-season play-offs for the first time in 15 years, the same year they won the title in 2006.
Sale director of rugby Alex Sanderson said a lot of the credit for the club's form is down to the advice injury-plagued England centre Manu Tuilagi is giving the younger players.
Tuilagi made his first appearance in almost eight months as a replacement on Friday.
"He's (Tuilagi) the glue in the team," said Sanderson.
"He spends more time with the younger lads than he does the senior boys.
"People rally to him because of the bloke he is, not just the player."