Millwall boss Kenny Jackett praised his defenders after an impressive 3-0 win away at Doncaster boosted their Championship survival prospects.
Andy Keogh was left unmarked to head home the opener from six yards, while goalkeeper Carl Ikeme should have done more to keep out Harry Kane's speculative long-range effort for the second.
By the time Darius Henderson added a third for Millwall after the interval, there was an uneasy atmosphere at the Keepmoat Stadium, with sections of the home support making their feelings clear.
Lions manager Jackett said: "It was a vital game tonight against one of our competitors at the bottom, to not let them come back at us.
"We've very pleased with the result, first and foremost, and the performance was good. Defensively we were solid and going forward we worked their keeper well and created a number of chances.
"Portsmouth had a good win, and obviously Forest (who won 7-3 at Leeds), so it was vital that we did win because people can come back at you."
Doncaster boss Dean Saunders was furious with the abysmal marking that led to Keogh and Henderson getting on the scoresheet.
"It was just soul-destroying because we train every day and we go over things like that," he said. "You are taught when you are 10 to mark strikers in the box and it's not rocket science - there's a ball coming in from out wide, you mark the centre forward. Andy Keogh gets a free header in the six-yard box and then Henderson gets a tap-in at the near post.
"When you spend hours on the training ground and you go over the basics (it is frustrating). We go over it and over it."
