A win over Moldova on November 12 would be enough to secure second place in Group F and a spot in the World Cup play-offs. Failure to do so could take it to a nerve-shredding final match against group winners and already qualified Denmark at Hampden three days later.
Given the Danes' form - they are the only European nation with a 100 per cent record in qualifying after eight wins from eight – Scotland would much prefer to get the job done in Chisinau.
Only one problem... they will have to do so without the talismanic Lyndon Dykes, whose goals have made the difference throughout Scotland's qualifying campaign, including his late winner in the Faroe Islands last month. A booking in that 1-0 victory will see the QPR striker serve a one-match ban in Moldova.
Clarke will be keeping everything crossed that Southampton's Che Adams comes through the next two weekends of Premier League action unscathed as he will almost certainly lead the line in Dykes absence after scoring his first goal of the season in the EFL Cup defeat to Chelsea at Stamford Bridge on Tuesday.
The dilemma for the Scotland boss will be who partners Adams in attack.
Kevin Nisbet has gone off the boil at Hibs and, if based on form, may even struggle for a call-up this time around after featuring in every squad since making his international debut in March.
Ryan Christie would have been an option were he not suspended as well, but in any case he isn't a natural striker, as was shown when he partnered Dykes in the Faroes but rarely ventured inside the penalty box. Ryan Fraser falls into the same bracket. Clarke could even go back to Oli McBurnie, but that would be an unpopular call with the Tartan Army.
The answer could lie in the United States of America.
Johnny Russell has been Scotland's forgotten man since dropping out of the international picture under Clarke.
His last cap came in October 2019 as a substitute in a 6-0 win over San Marino at Hampden. Quarantine restrictions meant he was effectively unavailable for selection throughout 2020 and resulted in him being overlooked for the Euros.
Out of sight, out of mind can be an issue for Scotland hopefuls playing beyond UK shores - just ask Ryan Gauld - but Russell has issued a timely reminder of his goalscoring ability with an explosive streak for Sporting Kansas City.
A run of 10 goals in eight consecutive games has catapulted the former Dundee United and Derby forward above John Spencer as the top scoring Scot in the history of the MLS.
A stunning brace in Wednesday's 2-0 win over LA Galaxy took his tally to 39 goals for the club - two more than Spencer's previous record of 37.
A glance through his recent showreel shows a variation of top quality finishes. The 31-year-old is not so much knocking on Clarke's door as battering it down and barging in.
With the pedigree of 14 caps and his first Scotland goal already behind him, Russell should be rewarded with a seat on the plane to Moldova. We are not in a position to overlook an established international in red hot scoring form.