Sunderland survived a scare against Barnsley to secure a huge win in their promotion push.
Here's what we learned from the 4-2 win at the Stadium of Light.
Sunderland's flexibility proving a key weapon
Jack Ross isn't afraid to make bold decisions, whether it be in his team selection, shape or substitutions during the game.
And the 4-2 win over Barnsley was no different, with Ross surprising most with a new-look and very fluid 4-3-1-2 system.
By his own admission, Sunderland were vulnerable defensively with so much emphasis going the other way.
But brave Ross backed his forward players and they repaid that faith, Sunderland 3-0 up within 32 minutes. It could - and should - have been more, Josh Maja missing two headed chances.
The system freed up Aiden McGeady and he enjoyed a barnstorming game, scoring his fifth in six games.
Adam Matthews' influence in this Sunderland side grows each week.
League One's very own Cafu. And that's only being slightly tongue in cheek.
Matthews has been excellent since Ross switched to a flat back four and his willingness to do the hard yards and get forward at every opportunity is great to see, adding another dimension to what is already a very attacking Sunderland side.
During the first half especially, Barnsley struggled to cope with him and his ball into Maja for the striker's 11th of the campaign was sublime, pinged forward at pace with the outside of his boot.
Maja finished the chance superbly. Reece James on the other flank also deserves credit for his recent performances, keeping Bryan Oviedo out of the side.
Max Power bounces back strongly after turbulent 48-hour spell.
What a few days it has been for the Sunderland midfielder, shown his third red card of the season at Walsall.
It was then overturned by the FA on Monday, Power avoiding a five-game ban.
Power was then named in the starting line-up to face promotion rivals Barnsley on Tuesday night, playing in the holding role in front of the defence, Power excelled.
Composed, he helped dictate play and he can certainly pick a pass. Not his usual role which sees him further up the pitch but he executed his new role well.
Aiden McGeady proving why he is one of the best players in League One.
Given his quality and pedigree, McGeady should be one of the best players in League One and he is proving it since returning to the Sunderland side after injury.
The Republic of Ireland international has five goals in his last six league games for the Black Cats and his quality again shone through against Barnsley.
He won and then scored the penalty and calmly picked out Luke O'Nien for the fourth goal.
Earlier, his whipped in cross was perfect for the diving head of O'Nien but he could only steer it wide of goal.
The cross deserved more. Sunderland are blessed with an array of attacking talent and McGeady is currently the pick of the bunch.
Luke O'Nien pushing hard for a start.
Ross was keen to stress post match that he doesn't consider O'Nien a super sub, adding he has much more to offer than that, but he has certainly made a big impact from the bench in recent weeks.
It was a big call for Ross to take Maja - who was also struggling with a shoulder complaint - off before the hour mark and replace him with O'Nien, especially with Jerome Sinclair also on the bench.
It paid off handsomely.
O'Nien's energy and willingness to make those runs into the penalty area eventually paying off. Another shrewd move by Ross.
Portsmouth show no signs of slipping up.
Pompey were the early pacesetters in League One and they continue to set the standard.
They won again on Tuesday night, making it three straight wins in the league, maintaining their four point lead over the Black Cats.
Sunderland moved five points clear of Barnsley but Luton Town and Peterborough United are still breathing down the neck of Sunderland.
The Black Cats are unbeaten in 14 games in all competitions and they must maintain those high standards to achieve promotion this campaign.
League One is proving relentless and fiercely competitive.