Glasgow Rangers have now suffered back-to-back defeats, with the Ibrox side losing 2-1 away at Dundee on Friday night.
Graeme Murty would have been hoping for a reaction from his players after the Gers suffered a disappointing 2-0 defeat at home to Hamilton last weekend - but unfortunately for the away fans at Dens Park, it was Neil McCann's men who were celebrating victory at the final whistle.
The Scottish Premiership strugglers lifted themselves off the bottom of the table as they won 2-1 to deny Rangers the three points that would have taken them second in the table, and now leaves the door open for their rivals to put more daylight between themselves and the Gers.
And after the game, Jack - who was visibly angered at the result and the manner of it - did not hold back in his assessment of the performance.
"There's no way we can hide from it, it's so frustrating as players, as a group it's just not good enough. I think we're letting everyone down, we've also let the fans down. What a support we had through the day, and [it's] their right to [direct] anger and frustration at us. As players, we're feeling it but it's not good enough."
While Rangers' managerial situation can be deemed a factor for their struggles in the last two games, few supporters will surely allow the players to argue that not having a permanent boss is the main reason for their recent woes, and it appears that the players have no plans to use that argument anyway.
The squad is certainly good enough to beat a Dundee side that had won just twice in the league all season before Friday, and had not tasted victory in any competition since the end of September.
But a sloppy performance opened the door for Dundee to capitalise, and they took full advantage, securing what will be a huge win for their confidence.