Makenzie Kirk's early strike helped St Johnstone banish their Premiership blues as they earned a first home win over Motherwell in three years to claim a place in the Scottish Cup last 16.

A whirlwind start brought Kirk's goal inside the first 10 minutes, scrambled in from a Graham Carey corner.

The legs of Motherwell keeper Archie Mair then prevented debutant Victor Griffith from doubling the advantage shortly afterwards when he was sent clear on goal.

Had Simo Valakari's side been tidier with their finishing, their win could have been a whole lot more comfortable.

They were unrecognisable from the side who had lost seven of their previous nine and are adrift at the bottom of the league.

A fabulous effort from the edge of the area from Graham Carey's left boot nearly gave St Johnstone the insurance their play deserved but his shot crashed off Mair's right-hand post.

Motherwell looked a shadow of their normal selves, although will point to the absence of nearly a full team due to injury.

Striker Tawanda Maswanhise had a great chance to equalise in the first half but shot tamely Andy Fisher, while some calamitous home defending nearly gift-wrapped an equaliser before the ball was hacked clear.

Motherwell improved after the break, but even some intense late pressure was not enough to deny St Johnstone their first win since 23 November or a place in Monday's draw.

The Motherwell fans made up half the crowd and gave vent to their feelings with a furious round of booing on the full-time whistle.

St Johnstone manager Simo Valakari: "It's a big win for the players, for the club and for the fans as well.

"The most important thing today was to win the match and get to the next round but the first half performance was very good and in the second half we showed the character to defend.

"It has not been easy, there's no hiding but you cannot control the results. You can control the performances and I thought the players put in a good performance today."

Motherwell manager Stuart Kettlewell: "I'm really disappointed.

"I didn't feel we started the game at all and let St Johntsone impose themselves on us.

"We lacked the body language at times to take part in the game and if you do that against any opposition you're going to find it difficult."