Nigel Clough has not been surprised by the way Millwall have risen to the Championship challenge in "brilliant" fashion this season.
The Lions reached the second tier via the League One play-offs in 2016-17, having only secured the last top-six spot on the final day of the campaign.
They have not looked back, taking to Championship life seamlessly and winning a third of their 33 games so far.
When the sides meet at the Pirelli Stadium on Saturday, Millwall will sit 13th, closer to the top six (nine points adrift) than the relegation zone (16 points clear) - and having won three of their last four League matches.
Clough knows all too well the challenge that awaits.
Asked if the Lions' relative success this season straight out of League One has come as a shock, he said: "No, not at all, having seen them last year in League One.
"They've kept pretty much the same team but just added a few - the quality, that's been the key.
"They've kept the squad together and they've risen to the challenge.
"Nobody enjoys going down to Millwall, so to have that advantage, they make full use of it.
"They're a very, very good, organised team.
"They are a strong and aggressive team. They completely play to their strengths and what a brilliant first season they've had back in the Championship.
"They're just about safe now, with a dozen or so games to go.
"I think that says an awful lot about how well they've done."
Burton have fared less well thus far, although recent performances and results have reenergised their survival bid, helped in part by a newfound solidity across the pitch.
While the 59 goals conceded by the Brewers after 33 games is the worst tally in the league, they have shipped only one in their last three outings.
Millwall will certainly test Albion's defensive credentials if they are to maintain that solid run, though.
"I think they've probably got one of the most dangerous forward lines," added Clough of the visiting Lions.
"They've got Lee Gregory, Steve Morison and Tom Elliot - they're capable of scoring goals.
"You have to be able to deal with that first and foremost. They're uncompromising, full of running.
"They are a very honest team and very difficult to play against."
Last time Millwall visited the Pirelli, it was a League One clash on December 1, with first-half goals from Damien McCrory and Nasser El Khayati setting Albion on the way to a 2-1 win.
A week later, Jimmy Floyd Hasselbaink had left for Queens Park Rangers and Clough was back in charge of the Brewers.
