Victory for the visitors would have ensured Premier League football for next season, while the Tykes began the day in the relegation zone.
It was a nervy display by Steve Bruce's men, while it was a huge boost for Barnsley and Flitcroft said: "It's massive, isn't it?
"I think the occasion - the last home game - again we're only two weeks away from getting crushed and in a lot of people's minds the season was over against Charlton.
"The courage, the bravery they've displayed; but also the quality was on show. That was evident today."
With one game remaining, it may work out that Barnsley do not need all the spoils at Huddersfield next weekend to survive.
But a reinvigorated Flitcroft said his team now had "ridiculous momentum".
"If we turn up with that energy we're going to be a match for anyone in this division and that's what we've certainly showed since I took the job," he said.