THERE was a time when Hampden spooked Celtic. Such was the exorcism conducted by Brendan Rodgers in his inaugural season at the Parkhead club that Celtic haven’t just killed off any haunting memories from the national stadium, but appear to have banished any domestic tournament from taking place without them holding fort.

Neil Lennon’s side will face Aberdeen in April in the semi-final of the Scottish Cup as they took a further step towards a quadruple Treble. Here are five things we learned as they progressed at St Johnstone’s expense.

Conditions were far from ideal

Reluctant to state the obvious but soggy, muddy pitches make for games that are just as heavy on the eyes as they are on the legs. Underfoot conditions weren’t great and aided by a swirling wind, it was never conducive to much of a game.

The combination of the pitch and the effects of Thursday night’s game on Celtic suggested there were a few weary limbs on show. It made for a turgid encounter at times with players skidding around and the ball too often held up by the weight of the mud.

Crime and punishment?

The penalty system doesn’t reflect well on the nature of the crime. Fraser Forster went into the book in the final minutes of this game after he took exception to a hefty, high kick on Christopher Jullien from St Johnstone’s Liam Gordon.

The latter’s actions were a fairly clear-cut case of reckless play but that both players copped the same punishment for fairly different offences seems harsh.

Celtic need Christie

Ryan Christie’s return to the Celtic starting line-up gave the Parkhead side energy and verve. It was the midfielder’s free-kick that led to the only goal of the game and although it looked as though Jullien had claimed his eighth goal of the season, the defender himself seemed keen that the credit for the goal was given to his team-mate.

Although as Lennon was keen to point out after the game, it was the defender’s run that made the goal whether he was the last player to touch the ball or not.

Tired Celtic still got over the line

Celtic still looked hungover from their midweek European defeat to Copenhagen but it is impossible to ignore the relentlessness of their current domestic cup run.

The win at McDiarmid Park yesterday afternoon was their 34th successive win and takes them to Hampden for the 15th team in four seasons. The Parkhead side seem capable of grinding the wins out even if they are not firing on all cylinders.

Lennon will have to rotate his squad

There could be a few changes made to Celtic’s starting line-up for the midweek game against Gary Holt’s Livingston side. A few of the Parkhead side look tired in the aftermath of what has been a fairly relentless schedule since the return from the mid-season break in Dubai.

Odsonne Edouard and Leigh Griffiths have linked well at times as they try to form a front pairing but both looked a little flat in Perth. A tweak wouldn’t be the biggest surprise ahead of the trip through to the West Lothian stadium.