The hosts are sitting in third position with seven points to their name, while the visitors are one point better off in second place in Group F.
Match preview
St Johnstone face a real fight to reach the knockout rounds despite beginning their campaign with consecutive victories over Brechin City and Greenock Morton.
However, their last-16 hopes were dented in midweek when they fell to a narrow 3-2 defeat in their away clash with third-tier Alloa Athletic.
Benjamin Mbunga Kimpioka restored parity just one minute after Morgyn Neill had opened the scoring, before Inverness midfielder Aaron Essel was given his marching orders.
Alloa ultimately made full use of the numerical advantage, with Luke Rankin scoring a five-minute brace before Jack Sanders netted a late consolation, as the Saints fell to their competitive defeat of the season, leaving them one point behind East Fife and two points adrift of Alloa.
St Johnstone will know that a win on Saturday would give them a strong chance to progress as at least one of the best second-placed sides, but a failure to secure all three points will result in their elimination.
East Fife entered the final group game with a real chance to qualify for the League Cup knockout rounds for the first time since 2019-20.
Dick Campbell's side began their League Cup campaign with a commanding 3-0 win over Greenock Morton, before they played out a goalless draw with Alloa Athletic and then lost the subsequent penalty shootout to miss out on a bonus point.
They swiftly returned to winning ways with a commanding 4-0 victory in Saturday's home clash against Brechin City, which came courtesy of a Nathan Austin brace and efforts from Liam Newton and Scott Shepherd.
Having recorded three consecutive clean sheets, East Fife will hope to produce another strong defensive display in their first competitive meeting with St Johnstone since July 2018.
East Fife will finish top if they claim all three points and Alloa fail to beat Greenock Morton, while a point will be enough to secure a top-two finish and put them in contention to clinch one of the best second-placed spots.
St Johnstone Scottish League Cup form:
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East Fife Scottish League Cup form:
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Team News
The hosts are likely to be without Uche Ikpeazu and Nicky Clark due to injury, while Essel will miss out through suspension.
St Johnstone boss Craig Levein could offer starting opportunities to Matt Smith, Sven Sprangler and Graham Carey.
Forward Mbunga Kimpioka will be looking to continue his fine form after scoring three goals in the last two matches.
As for the visitors, Alan Trouten was a notable absentee from Tuesday's matchday squad, and the 38-year-old will have to be assessed ahead of Saturday's fixture.
After seeing his team sweep past Brechin, Campbell could be tempted to select an unchanged lineup for the final group game.
St Johnstone possible starting lineup:
Rae; Keltjens, McClelland, Sanders, Raymond; M Smith, MacPherson, Wright, Sprangler, Carey; Mbunga Kimpioka
East Fife possible starting lineup:
McFarlane; Murdoch, Munro, Easton, Peggie; Healy, Millar, Norey, Newton; Shepherd, Austin