Martin O’Neill knows how quickly the noise around Celtic can change.

A week that started with heavy criticism after the 4-1 defeat to Benfica ended with Celtic hammering Hearts 7-1 at Celtic Park and moving four points clear at the top of the Premiership.

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Celtic had been accused of stumbling after poor European results and a difficult run in bigger fixtures, but Sunday’s performance blew Hearts away before half-time.

Kieran Tierney opened the scoring, Benjamin Nygren made it two, and Callum Osmand struck twice on his first start.

Jamie McCart’s own goal made it 5-1 at the break, before Camilo Duran and Nygren added more in the second half.

After the match, O’Neill was asked whether the result sent a message to anyone talking about Celtic being in trouble.

Speaking at his post-match press conference, O’Neill said: (TCW), “If we lose on Thursday, it’ll be crisis back again. So, you know, been here before. Just have to try and win.”

That is the reality of Celtic right now.

The Hearts result was excellent, but Thursday night against Celta Vigo will quickly take over.

O’Neill has already said his side “need to win” that game, and he knows a league rout will only carry so much weight if Celtic fail to follow it up in Europe.

Celtic looked faster, sharper and far more ruthless than they did in Lisbon. Osmand and Haissem Hassan justified their starts after impressing from the bench against Benfica, while Duran made a strong case to keep playing through the middle.

The mood around the club will always swing quickly.

O’Neill knows that better than most.

Celtic have given themselves a lift. On Thursday, they need to make sure the crisis talk stays away.