Motherwell have their first real chance of the game and it comes on the break with Connor Shields racing down the line.

His shot was heading for the far corner but Morton keeper Jack Hamilton manages to get a hand to it.

Stunning double save from Darren Jamieson.

Firstly, the Kelty keeper is at full stretch to stop a glancing header towards the back post from Chris Kane.

Seconds later, Ali Crawford shapes on from outside the box to the top-right corner and again Jamieson is across to tip it away.

Kilmarnock defender Ash Taylor tries to atone for his earlier blunder, reaching a corner at the back post, but goalkeeper Benjamin Siegrist palms it away.

No attempts on goal so far at New Central Park, but cup holders St Johnstone are enjoying the majority of the ball.

Done nothing with it, though.

Both teams are trying to get on the front foot at Fir Park, with Morton giving a good account of themselves in the opening minutes.

No clear cut chances for either side yet.

Aberdeen threaten again. Ross McCrorie waltzes up the park and cracks one in from the edge of the box, but it's a comfortable save for Brian Schwake.

Moments later and and Teddy Jenks goes down in the box claiming for a penalty, but referee Alan Muir says no.

Ayr are on top early on as the home side impress through the smoke covering Somerset Park thanks to flares set off by the excited fans.

Jonny Hayes drills a shot just wide of the post as Aberdeen start brightly at Pittodrie.

Hearts, Rangers and Hibernian are all in the hat... Who's going to join them in the fifth round of the Scottish Cup?

Remember, no replays. It will be extra-time then on to penalties if we don't get a winning goal.

A delayed kick off at Holm Park as a big crowd squeezes into Holm Park.

Kilmarnock manager Derek McInnes tells BBC Scotland why new signing Kyle Lafferty is on the bench.

He explains: "We didn't get his registration through until late afternoon yesterday. He's not really trained with the lads. It's been quite a busy week for him. But he's ready, he's keen as mustard, and desperate to play his part.

"He gives us experience, a goal threat and personality.

"Maybe when Dundee United are on losing run, the last place they want to go is Rugby Park, but they maybe see it as a respite and they appear to have named an attacking team.

"The cup is very important. We want to be a strong cup team, I want the club to get a reputation for being a good cup team."

Image source, SNS

Martin Dowden
BBC Sport Scotland at C&G Systems Stadium

Six league defeats on the trot appears to have inspired James McPake to ring the changes and he has dropped a fair amount of experience to the bench today after saying some of them perhaps let him down midweek.

They badly need a smooth day at the office to settle things down and in Dumbarton they're not exactly facing a team high in confidence themselves but the hosts will know the pressure is all on Dundee here.

A cup shock on the cards? One Dundee fan on social media joked yes, Dundee might actually win! If they are to progress they will need to start on the front foot and give Dumbarton no encouragement.

The winner at Rugby Park may well come down to whose new star striker is on form.

The Scottish Premiership's top goalscorer Tony Watt makes his first start for Dundee United following his move from Motherwell, after a substitute appearance during the week.

Kyle Lafferty has returned to Kilmarnock after a spell in Cyprus, but has to make do with a place on the bench this afternoon.

Image source, SNS

Banks O’Dee: Hobday, Young, Lawrie, Kelly, Lewecki, Duff, Henderson, Gilmour, Macleod, Philipson, Alexander.

Substitutes: Armstrong, Crosbie, Allan, Macaskill, Watson, Robertson, Humeniak, Sweeney.

Raith Rovers: MacDonald, Dick, Williamson, Berra, Matthews, Zanatta, Lang, Stanton, Musonda, Ross, Gullan.

Substitutes: Thomson, Benedictus, Connolly, Snow, Arnott, Mitchell, Young, Poplatnik.

St Johnstone manager Callum Davidson tells BBC Sportsound that he's signed up defender John Mahon from Sligo Rovers and that midfielder Cammy MacPherson has been recalled from his loan at McDiarmid Park by St Mirren.