AFTER Friday night's defeat to Fulham as well as Derby's victory over Cardiff on Tuesday night, the Lions' trip to The Riverside has become even more of a must-win game in the race for the top six.
A win in the late kick-off could move Neil Harris' side back into the play-off positions if Derby fail to win at Villa Park.
Earlier in the season, Millwall beat Boro 2-1 at The Den in another impressive home victory over a multi-million pound side.
Three points on Saturday would mean that Millwall have eight wins in their last 10 away games, which is even more impressive when you consider that they hadn't won away until they faced Leeds at Elland Road on January 20.
Middlesbrough have changed managers since these sides last met, with Garry Monk in charge until December before he was sacked and Tony Pulis took over.
Pulis seems to be getting the best out of his players, in particular Adama Traore who needs to be stopped if the Lions are to have any chance of victory.
Lucas Ball spoke to Boro fan Josh Frankland this week.
Why do you support Middlesbrough?
They're my local team so I have naturally been brought up a Middlesbrough fan. All my family have supported Boro, there wasn't any chance I was dodging that!
What's been your favourite season following your side?
The 2014-15 season was pretty special. The entire season was amazing.
We were the best we'd been in the league for a long, long time. We even beat Manchester City in the FA Cup at the Etihad!
We had so many memorable moments and reaching the play-offs was great. It was just a shame we lost in the final, 2-0 against Norwich City.
Has it been a disappointing season overall for Middlesbrough given they were tipped to be automatic promotion contenders?
Up until two months ago, even one month ago, this was a very poor season – especially looking at how much we spent in the summer (over £40million). However, we have recovered it slightly by forcing our way into play-off contention.
Are you happy with the change in fortunes since Tony Pulis arrived?
I'm a huge fan of Tony Pulis, even the simple things such as the way he comes across in press conferences, he gets the fans and the club.
He's full of praise constantly and knows what he's saying, unlike the robotic Monk. On the pitch it's been much better too.
Muhamed Besic was a class signing, on loan from Everton, and Pulis has got the best out of Traore, from a player we were all writing off to a potential £30/40m player.
If Boro aren't to go up, which sides would you like to see promoted?
Wolves already have, thankfully – they deserve it.
Then I'd go for Fulham and Villa.
Who will be the danger men for the home side on Saturday?
Traore, without a doubt. He's on another level, I've never seen a player like him. Strikers Patrick Bamford and Britt Assombalonga are the other obvious shouts.
Similarly, which Millwall players will you be keeping an eye on?
Honestly, not a clue!
Very ignorant of me not to know much about Millwall. They do strike me as a team rather than having loads of class individuals.
Obviously we're going to expect a physical game. Everyone knows that's what Millwall are about.
What's your predicted starting XI and formation?
Randolph; Shotton, Ayala, Gibson, Friend; Howson, Clayton, Besic; Traore, Bamford, Downing.
Finally, a score prediction?
If we turn up and Traore is on form, I think we'll just about have too much.
I'll go with Middlesbrough 2-0 Millwall.