Amid a fixture list that Jose Mourinho bemoans as dammed and distorted, the next five days should prove decisive.
Twin tilts threaten to slip from grasp. On Tuesday, Tottenham Hotspur take on RB Leipzig in Europe, then host Manchester United in the Premier League on Sunday.
An exit from this season’s Champions League could precede a major setback in the fight to qualify for the next. One-nil down in their last-16 clash with Leipzig, and without a win in five matches, Spurs’ path to a second successive European Cup quarter-final is far from guaranteed.
Runners-up last time out, they might be run out this week.
It would hardly represent ideal preparation for United. In contrast to Spurs, the Old Trafford side are in rude health, invigorated by a run of 10 matches unbeaten that culminated in Sunday's inspired derby defeat of Manchester City.
Where United glow with late-season optimism - the FA Cup, the Europa League, a top-three finish in the Premier League - Spurs appear to mirror the mood of their manager. Mourinho can be dour and dismissive, wishing away the time until he can call upon, principally, Harry Kane and Son Heung-min.
Beset by injuries and understandable fatigue, Spurs look to have run out of steam as the campaign climaxes through its critical period.
Last week, the Londoners crashed out of the FA Cup. Offering their most obvious route to silverware, a fifth-round shootout loss to Norwich City made it four defeats on the bounce. It marked the worst spell since Mourinho took charge in November.
If the battling league draw at Burnley on Saturday then felt a point well gained, other results went against them. Of those involved in what has become a crowded Champions League chase, only Wolves, in sixth, failed to win.
With nine matches remaining - Sheffield United and Arsenal each have a game in hand - Spurs sit eighth, seven points off the top four. They have contested Europe's premier club competition for the past four years.
Eager to qualify again for the Champions League, their focus must fall first on extending their stay in this edition. It won’t be easy. Leipzig lie in wait, Julian Nagelsmann’s exciting and exuberant bunch who challenge still for the Bundesliga title.
Like Spurs, though, they have stumbled of late. Three draws from five matches have affected their domestic campaign, frustrated most recently by Bayer Leverkusen and Wolfsburg. The weekend draw at the latter meant Leipzig slid to third in the table, one point below Borussia Dortmund and five behind Bayern Munich.
Even though, in the first leg in London Leipzig were relatively untroubled, slicing through Spurs, despite modelling a makeshift backline. For the return at the Red Bull Arena, centre-back Dayot Upamecano is again available for selection.
Spurs, meanwhile, have added to their injury list winger Steven Bergwijn, perhaps Ben Davies, too. Crucially, Bergwijn’s absence limits further the options in attack.
On another note, what sort of reaction Mourinho's evisceration of Tanguy Ndombele extracts from the midfielder, if anything, remains a moot point.
With the manager, the temptation is to ascribe his finest performances to Champions League nights. He guided Porto to the crown in 2004, then Inter Milan seven years later. Both were achieved against considerable odds.
Even in those final few vexed weeks at United, when he appeared determined to force his departure, Mourinho masterminded a win at Juventus. How capable is he of coaxing a similar display now? How able are Spurs of reproducing last year’s heroics in Europe? Back then, just before they dispatched Dortmund and annexed Ajax, they had struggled as well.
Of course, Mauricio Pochettino has since gone. His successor, Mourinho must once more prove a master alchemist. Beginning with Leipzig, and continuing quickly against his previous club, the next five days demand it.