Millwall manager Gary Rowett was impressed with how his side nullified Brentford's attacking threat after claiming a 1-0 win at the Den.
Aiden O'Brien scored his fourth goal of the season in the eighth minute when Jayson Molumby forced Bees goalkeeper David Raya into a mistake which left the striker able to slot home into an empty net.
With one loss in their last 10 matches, Millwall's run of form has moved them to within two points of the Sky Bet Championship play-offs.
Rowett changed the way he would normally set up his side at home and was pleased they could get the better of their fellow promotion hopefuls.
"I thought the first half had some really good stuff," he said. "It's the first time we've played a five (at the back) system at home, we've obviously played it very effectively away, and I felt as though we nullified their clear chances very well.
"I think Barts (Bartosz Bialkowski) made one good save but other than that I felt we kept them at bay very well and should have had some more opportunities of our own.
"They are a good side, Brentford. For them to be so free-scoring – probably the form team in the division, I'd say – he's (Thomas Frank) done a brilliant, brilliant job.
"I know they had a slow start to the season but they have really kicked into gear so they're a difficult side to stop and it causes you one or two problems in terms of how you structure your own team."
It was a frustrating afternoon for Frank's men, who have not won on the road since their 3-0 victory over Wigan in November.
Despite his goalkeeper making an error which led to the goal, Frank was clear that Brentford will continue playing out from the back and will not change after one mistake.
"I think Millwall created several chances in the game, we gave them the goal," he said. "It's no secret that David made a mistake but I think he's been absolutely amazing this season.
"For me, he's potentially the best keeper in the division. Football is a game of mistakes, that happens, we'll move on.
"I think we've played out from the back so far in, what, 25 games? We made one mistake that cost a goal and I'd happily take that risk because it gives us an advantage.
"The rest of the game we were chasing and Millwall made it difficult for us. We also need to give them a bit of credit for that because normally we are extremely dangerous going forward."