Keanu Baccus is back in the St Mirren starting line-up after being off on international duty with Australia in the Asian Cup.
James Bolton was sent off in the midweek win against Dundee so he's out today as is James Scott and of Kwon Hyeok-kyu is unable to play against his parent club. Charles Dunne and Lewis Jamieson are in.
Brendan Rodgers has switched things up with a 4-2-2 formation, and the big news is Kyogo Furuhashi is back after starting on the bench in the win against Hibs. He partners birthday boy Adam Idah up top.
Tony Ralston is in for the injured Alistair Johnston and Luis Palma tags out Nicholas Kuhn, while Paulo Bernardo also drops to the bench.
SNSCopyright: SNS
Kyogo is starting in a front two for CelticImage caption: Kyogo is starting in a front two for Celtic
Post update
Quite the stat: Brendan Rodgers has never lost a Scottish Cup game.
Does that continue or end today?
SNSCopyright: SNS
Best of the action so far
From wild scenes at Cappielow and bedlam at Firhill, to a clinical double from Bojan Miovski...
Catch up with the best of the weekend action so far by bashing those play buttons below.
Video content
Video caption: Watch the full-time scenes as Morton secure quarter-final spotWatch the full-time scenes as Morton secure quarter-final spot
Video content
Video caption: Watch Bojan Miovski's double against Bonnyrigg RoseWatch Bojan Miovski's double against Bonnyrigg Rose
Video content
Video caption: Watch Livingston complete comeback with extra-time winner at Partick ThistleWatch Livingston complete comeback with extra-time winner at Partick Thistle
Post update
Sportsound is on air 🚨
Unconvinving Celtic face tough Paisley test
St Mirren v Celtic (14:00)
Celtic are getting by, but they've looked a bit out of sorts recently.
A trip to Paisley wasn't the kindest of draws, given St Mirren took four points off the champions last season.
But Stephen Robinson's side took three hidings in between and have lost both league meetings this time round.
Celtic have been unconvincing since the campaign resumed, enduring uncharacteristic struggles in front of goal.
St Mirren will have noted how Hibs and Aberdeen gave the Scottish Cup holders a fright in the past week when having a go, but that's easier said than done.
St Mirren 'probably the toughest team' Celtic could face
St Mirren v Celtic (14:00)
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Celtic manager Brendan Rodgers tells BBC Sportsound: "This is a tough game for us, and a big one. We want to get through and to do that we'll need to give 100% in everything we do. This is probably the toughest team we could have faced in this moment.
"Over the course of the season, our performances have been a little inconsistent, so the aim is to continue to work on that, but in a cup game it is just all about getting through.
"If we're a team that aren't running, we're lost, so we need to run and break lines and get in behind. When we do that, we look a really good side.
"We will press in our normal structure, as we do in a 4-3-3, so it's just a slight adaptation [going to a 4-4-2]."
Listen live on Sportsound
BBC Radio Scotland
We've been treated with a bumper Sportsound today.
There will be over six hours of radio coverage on BBC Radio Scotland, starting from 13:30 GMT.
The gang will provide live commentary from Paisley and Airdrie.
Live Reporting
Nick McPheat
All times stated are UK
Baccus back for St Mirren; Kyogo starts with Idah
St Mirren v Celtic (14:00)
Big players return for a big game.
Keanu Baccus is back in the St Mirren starting line-up after being off on international duty with Australia in the Asian Cup.
James Bolton was sent off in the midweek win against Dundee so he's out today as is James Scott and of Kwon Hyeok-kyu is unable to play against his parent club. Charles Dunne and Lewis Jamieson are in.
Brendan Rodgers has switched things up with a 4-2-2 formation, and the big news is Kyogo Furuhashi is back after starting on the bench in the win against Hibs. He partners birthday boy Adam Idah up top.
Tony Ralston is in for the injured Alistair Johnston and Luis Palma tags out Nicholas Kuhn, while Paulo Bernardo also drops to the bench.
Post update
Quite the stat: Brendan Rodgers has never lost a Scottish Cup game.
Does that continue or end today?
Best of the action so far
From wild scenes at Cappielow and bedlam at Firhill, to a clinical double from Bojan Miovski...
Catch up with the best of the weekend action so far by bashing those play buttons below.
Video content
Video content
Video content
Post update
Sportsound is on air 🚨
Unconvinving Celtic face tough Paisley test
St Mirren v Celtic (14:00)
Celtic are getting by, but they've looked a bit out of sorts recently.
A trip to Paisley wasn't the kindest of draws, given St Mirren took four points off the champions last season.
But Stephen Robinson's side took three hidings in between and have lost both league meetings this time round.
Celtic have been unconvincing since the campaign resumed, enduring uncharacteristic struggles in front of goal.
St Mirren will have noted how Hibs and Aberdeen gave the Scottish Cup holders a fright in the past week when having a go, but that's easier said than done.
St Mirren 'probably the toughest team' Celtic could face
St Mirren v Celtic (14:00)
Celtic manager Brendan Rodgers tells BBC Sportsound: "This is a tough game for us, and a big one. We want to get through and to do that we'll need to give 100% in everything we do. This is probably the toughest team we could have faced in this moment.
"Over the course of the season, our performances have been a little inconsistent, so the aim is to continue to work on that, but in a cup game it is just all about getting through.
"If we're a team that aren't running, we're lost, so we need to run and break lines and get in behind. When we do that, we look a really good side.
"We will press in our normal structure, as we do in a 4-3-3, so it's just a slight adaptation [going to a 4-4-2]."
Listen live on Sportsound
BBC Radio Scotland
We've been treated with a bumper Sportsound today.
There will be over six hours of radio coverage on BBC Radio Scotland, starting from 13:30 GMT.
The gang will provide live commentary from Paisley and Airdrie.
LINE-UPS from Dens Park
Dundee v St Johnstone (14:00)
Dundee: Carson, McGhee, Sylla, Shaughnessy, Donnelly, Beck, Cameron, Tiffoney, McCowan, Bakayoko, Robinson.
Substitutes: Sharp, Dodgson, Astley, Lamie, Ashcroft, Mulligan, Robertson, Mellon, Costelloe.
St Johnstone: Mitov, Olufunwa, K Smith, Considine, Gordon, Robinson, M Smith, Kjeltens, Carey, Kimpioka, Sidibeh.
Substitutes: Richards, Gallacher, McGowan, Kane, Clark, Jaiyesimi, Kucheriavyi, Sprangler, C Smith.
LINE-UPS from Smisa Stadium
St Mirren v Celtic (14:00)
St Mirren: Hemming, Fraser, Gogic, Dunne, Bwomono, Baccus, Boyd-Munce, Tanser, Kiltie, Mandron, Jamieson.
Substitutes: Urminsky, Taylor, Brown, Flynn, Mooney, Penman, Olusanya, Scott, Ayunga.
Celtic: Hart, Ralston, Welsh, Scales, Bernabei, McGregor, O'Riley, Palma, Maeda, Idah, Kyogo.
Substitutes: Bain, Kuhn, Yang, Nawrocki, Oh, Iwata, Bernardo, Vata, Kelly.
Post update
Line-ups, anyone?
🍽 Your Sunday menu
Scottish Cup:
Scottish Premiership:
Post update
Three games, two competitions and a cup draw.
As far as Sundays go, I reckon we're in for a pretty decent one.
Scottish Cup last-16 weekend comes to an end with two belting ties, plus we have a top-flight Tayside derby at Dens Park.
Bliss.