Ange Postecoglou's side remained nine points clear of second-placed Rangers with a 3-0 beating of Livingston on Wednesday, while their hosts also picked up three points in their trip to Motherwell.
Match preview
After a positive run of form late last year took them onto 24 points from 17 Scottish Premiership outings, St Johnstone would have to endure a tough losing run, beginning with a 4-1 beating at the hands of Celtic before Christmas.
Callum Davidson's men were unable to bounce back from that result as they went on to suffer defeats to Hearts, Dundee United and Aberdeen, before the run was stretched to five games as they were beaten 4-2 at home to Livingston.
In their bid to make a return to winning ways, the Saints then faced a tough test against Rangers at Ibrox last weekend and again left empty-handed as Glen Kamara and James Tavernier got on the scoresheet in a 2-0 home triumph, leaving them towards the bottom end of the division with their tally still at 24 points after 23 matches ahead of a crucial contest away at fellow strugglers Motherwell on Wednesday.
Drey Wright gave Davidson's men the perfect start in that game, putting them ahead inside five minutes, and after Melker Hallberg doubled the lead early in the second half, they would stand strong to see out an eighth league win of the campaign and halt their slide.
With that result increasing their cushion over the bottom two back to seven points, the Saints will now be keen to build an improved run and continue climbing back up the Premiership table, but they face another particularly difficult test at the weekend as the league leaders arrive in Perth.
In their bid to retain the Scottish Premiership title this season, Ange Postecoglou's men have continuously kept themselves at the summit of the division and now find themselves unbeaten in 17 league matches since the beginning of October, when they suffered their only league defeat of the campaign thus far at the hands of St Mirren.
Of those games since that slip-up, the Glasgow outfit have added 16 further notches to their wins column, firstly putting 12 straight three-point hauls together before keeping rivals Rangers at bay as Kyogo Furuhashi levelled the Old Firm Derby at two goals apiece in the dying minutes after the turn of the year.
The Bhoys have kept up their relentless form since that share of the spoils at Ibrox, winning each of their last four league games without conceding a single goal and scoring 11, while also advancing to the Scottish Cup fifth round with a 5-0 thrashing of Greenock Morton, in which Aaron Mooy and Furuhashi both netted braces alongside a David Turnbull goal.
Following that resounding win and a 2-0 triumph away at Dundee United, and with Rangers remaining consistent in their bid to bridge the gap to top spot, Celtic were most recently in action at home to Livingston on Wednesday, and they continued their eye-catching run with another three-point haul, as Greg Taylor and Daizen Maeda had them two goals ahead inside 33 minutes, before Furuhashi again got on the scoresheet on the stroke of half time in an eventual 3-0 win.
Now sitting on 67 points from their 24 league matches, with only two blemishes on their record and a nine-point lead over their second-placed Old Firm rivals, Postecoglou's men will aim to further strengthen their position and continue a march towards what would be their 53rd Scottish top-flight title.
St Johnstone Scottish Premiership form:
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W
St Johnstone form (all competitions):
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L
W
Celtic Scottish Premiership form:
W
D
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Celtic form (all competitions):
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Team News
St Johnstone will have to make a change at left-back on Sunday, as Celtic loanee Adam Montgomery is unable to play against his parent club, with James Brown expected to fill in in a makeshift role in his absence, while Andy Considine, Liam Gordon and Alex Mitchell will all keep their places in the middle of the defence after the clean sheet against Motherwell.
Melker Hallberg will continue to play an important role in midfield after hitting his third goal of the season in that win, with Daniel Phillips and Cameron MacPherson again set to join him in the engine room.
At the top end of the pitch, Stevie May and Nicky Clark should continue their partnership in attack, having each netted four Premiership goals so far this season, with May also contributing six league assists, while Drey Wright had also found the net four times in Scotland's top flight and will offer further threat from a wing-back role.
Ange Postecoglou has little reason to change his Celtic team after their 3-0 victory last time out, although he may make some rotations given the strength throughout their squad, with the likes of Aaron Mooy, David Turnbull, Liel Abada and January signing Oh Hyeon-gyu all fighting to feature from the outset on Sunday.
Kyogo Furuhashi will continue to lead the line, after hitting his 18th league goal of the season against Livingston, while Daizen Maeda is vying to keep his spot in the front three after also getting on the scoresheet in that game, as is Jota who has netted seven goals and provided seven assists in 22 Premiership appearances this term.
Elsewhere, the Bhoys should go with an unchanged back four featuring Cameron Carter-Vickers and Carl Starfelt in the middle and Greg Taylor and Alistair Johnston on the left and right respectively, in front of stopper Joe Hart, while Callum McGregor should again feature in the engine room and don the captain's armband.
St Johnstone possible starting lineup:
Matthews; Wright, Mitchell, Gordon, Considine, Brown; Phillips, Hallberg, MacPherson; May, Clark
Celtic possible starting lineup:
Hart; Johnston, Carter-Vickers, Starfelt, Taylor; Mooy, McGregor, Hatate; Jota, Furuhashi, Abada