There was a time not too long ago where it seemed nearly impossible that this would end up as a Championship play-off semi-final.
Middlesbrough spent more days in the top two than any other club this season, while Southampton were labouring in the bottom half of the table midway through the campaign.
But here we are, fifth versus fourth at the Riverside, with the Saints somehow marching above Boro and going into this tie as slim favourites.
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'Neither side are capable of playing safe football'
Don Goodman on the Sky Sports Essential EFL podcast:
From about 17 games to go, Southampton were probably the best team in the league.
But then if you go back about 10 games before that, I would have been arguing at that point it was Middlesbrough. They won six in a row playing some of the best football I'd seen in the Championship.
If they both hit their levels, I couldn't tell you who would win.
Middlesbrough and Southampton have many things in common, but the biggest one is that I haven’t seen either of them play a dull, boring game. I don’t think they’re capable of playing safe football.
They have a very distinct way of trying to win games and I don’t think either coach will alter that. I can’t imagine Southampton going to the Riverside and setting up in a low block, so I think we’re going to get two really good games.
Andy Hinchcliffe on the Sky Sports Essential EFL podcast:
I just hope it’s the kind of free-flowing attacking game these sides are capable of producing. There are so many in-form goalscorers on both sides, and a lot of attacking talent. That’s what makes it exciting.
Southampton are the form side in the Championship. You look at the last six games and beyond, they’re the best side at the moment. The question is whether they can reproduce that over two legs.
Middlesbrough have the quality and experience to reset after missing out on the top two. This could be a really attractive couple of games and it’s very difficult to decide between them.
Middlesbrough were creating chances but not taking them, and that’s why they fell away. Now they are starting to take those chances, which will worry Southampton.
If Southampton play in an open, attacking way, that could play into Middlesbrough’s hands. That’s what makes it so tight to call.
To boo, or not to boo? The Azaz factor...
And then there is Finn Azaz, who swapped Middlesbrough for Southampton at the start of this season.
He started slowly, as did most of the Saints, but has emerged as one of their key men in attack. His reception at the Riverside, just as it was back in January, will be frosty at best.
"Finn Azaz is probably the player under the most scrutiny," Andy Hinchcliffe told the Sky Sports Essential EFL podcast. "He hasn't produced as much as he might have this season but he has the quality to turn games. It's about whether he rises to the occasion, and I'd expect him to.
Don Goodman added: "If I could give Middlesbrough fans any advice, it would be to not boo. Being booed can motivate players, it motivated me as a player, and it could inspire someone like Azaz. He's one of many players with the ability to decide a game."
The key battle: Scienza vs Brittain
Sky Sports EFL editor Simeon Gholam:
Southampton possess a depth of attacking strength but there is little doubt their superstar is Leo Scienza.
Even during the struggles in the early part of the season, the Brazilian winger was excellent. He has the kind of ability that can decide a game of this magnitude on his own.
He has the third-most assists in the Championship this season (10), the most big chances created (21) and the third-most successful dribbles.
Trying to stop him will be Callum Brittain, Middlesbrough's right wing-back who has enjoyed an exceptional campaign of his own.
He has the most dribbles of any defender in the Championship (53) and the fifth most crosses from open play in the Championship this season (178). Both will be trying to drive the other back down that flank, and it should make for a fascinating match-up.
Hellberg: The tie will not be decided on Saturday
Middlesbrough head coach Kim Hellberg will reiterate to his players that this semi-final will not be done and dusted in the first leg.
"You have to do it in a little bit of a different way," he said in his press conference on Thursday afternoon.
"The best way to say it is it's the first half of a game. That's the simple way of saying it, but it also means things.
"If it's 10 minutes left and you are one up or one behind, it's not the same thing as having 10 minutes left in a regular game, where you throw everything in different directions, depending on the score.
"That is the thing you need to be aware of. It's not a game that will be decided on Saturday as we will play 90 minutes more, then maybe extra-time on Tuesday.
"And then it's different playing against a team on Saturday and then the same team on the Tuesday. Only in the play-offs can you get to those types of games, where you play the same team so quickly after the first game."
Eckert: We will not play for a draw
Southampton head coach Tonda Eckert knows his side will have to stem Middlesbrough's flow at the Riverside if they are to take something from the first leg.
Having watched his side slump to a 4-0 defeat on Teesside back in January, Eckert will not be underestimating the challenge posed by Kim Hellberg's men.
"They have been quite clear in the way they approach the game. It is quite clear to see where they have their strengths," he said.
"If they catch a good day and they start to flow, they are a good team in certain aspects of the game.
"[But] we come from some good weeks and months. In the end it is about getting our strengths on the pitch like we have been doing for many weeks now."
With the second leg at St Mary's on Tuesday night, Saints could be forgiven for thinking that heading back down south with a draw would not be a bad result.
Eckert, though, insists that will not be in his team's mindset.
"No, that is not the way we approach games," he said. "At no part of the season has that ever been our approach, to draw a game. We will go there to win.
"We will do everything to win, and then we will see where we stand."
Championship play-off schedule
Play-off semi-final first legs
Play-off semi-final second legs
Play-off final