The one all-Premiership tie – and probably the least predictable – takes Dundee United to Motherwell on Friday evening in a meeting of two clubs looking to end a decades-long League Cup drought.
United have not lifted the League Cup since beating city rivals Dundee in the 1980 final, while Motherwell’s wait is even longer, having last won the trophy back in 1950, when they defeated Hibernian.
Indeed, neither side have gone beyond the quarter-finals since they last progressed to the final.
Motherwell defeated Aberdeen 3-0 seven years ago, before knocking out Rangers in the semi-finals and falling short in their bid for an Old Firm double against Celtic.
Two years earlier, United beat Hibernian on penalties after a 3-3 draw, overcame Aberdeen in the last four but also lost to Celtic in the final.
Celtic were also Well’s nemesis when the Lanarkshire side and United last reached the quarter-finals two years ago, the Glasgow visitors easing to a 4-0 win while the Tangerines were losing 2-1 in Kilmarnock.
The current sides go into Friday’s quarter-final looking to recover from top-flight defeats that ended three-game winning runs.
Stuart Kettlewell’s hosts fell 2-1 away to Aberdeen, while Jim Goodwin’s United had their impressive eight-game unbeaten sequence brought to an end by Rangers’ single-goal win at Tannadice.
Recent meetings are also no guide to Friday’s outcome considering United have spent a season winning the Championship since losing 3-2 at Fir Park in their last meeting – with United having won there a month previously.
Their knock-out meetings tend to be tight affairs too, with United winning 2-1 at Fir Park in the Scottish Cup fourth round in November 2014, while Alan Gow’s goal was enough to take hosts Motherwell through to the League Cup semi-finals in October 2010.
Another close game is in prospect under the Fir Park lights.