Manchester City have reached the tipping point, Chelsea clash is pivotal as Pellegrini and his men battle to overcome the numbers game
Manuel Pellegrini may want to pack a calculator along with his diary for Manchester City's trip to Chelsea, because if the Chilean is to pass on the baton to Pep Guardiola with a silver-plated legacy, he must master the numbers game which now threatens to ruin his team's pursuit of greatness.
Pellegrini's selection for tomorrow's FA Cup fifth round tie at Stamford Bridge, which kicks off less than 76 hours before a Champions League round-of-16 first leg against Dynamo Kiev, will give more than a nod to the intensifying demands on his players.
City face four games in four competitions over the space of 11 days, which will define their season.
Win them all, and tomorrow's trip to London could provide the spark which ignites a run of 27 games in 98 days leading all the way to the Champions League final in Milan on May 28.
But the flip side is a nightmare scenario of defeat at Chelsea, failure to win against Liverpool in the Capital One Cup final a week tomorrow at Wembley, followed by a potentially pivotal Premier League fixture at Anfield three days later.
If the worst comes to the worst, the Champions League second leg against Kiev on March 15 could be the last-chance saloon for Pellegrini, just as Guardiola prepares to put the final touches to his City plans.
For the first time since taking charge at City in the summer of 2013, Pellegrini will name a weakened team for tomorrow's clash.
The City manager has been criticised in the past for refusing to husband his resources in order to conserve energies, but members of the club's Elite Development Squad will be handed the chance to prove their worth.
Simon Davies, the head coach of City's EDS, said: "Some may travel to Chelsea, so this is a really important time for them. It's fantastic that they're getting their opportunity.
"If and when the opportunity comes they've got to take it because it's one of the best teams in England and Europe."
This was not supposed to happen, however. An FA Cup fifth-round tie against one of City's most formidable rivals should have been the occasion for Pellegrini's best players to hammer out the message that they are serious about achieving an unprecedented quadruple.
It is, after all, what the club's Abu Dhabi hierarchy laid out as the objective, with chairman Khaldoon al Mubarak insisting in his post-season review last June that four trophies could be won.
Al Mubarak said then: "We have a great nucleus here and we want to preserve this nucleus, but at the same time we want to go the next level. We want a squad that is able and has the capability and quality to win the Premier League, compete and win the Champions League, compete and be able to go all the way in two cup competitions in England."
Having added Raheem Sterling, Kevin de Bruyne, Nicolas Otamendi and Fabian Delph to Pellegrini's squad last summer, Al Mubarak reiterated the determination for City to pursue all four trophies when he spoke in the wake of the release of the club's accounts in October.
"No team can expect to win every year, but competing to win in England's domestic competitions and improving our performance in the Champions League are entirely reasonable goals," he said. "It is right to have high expectations."
But City are now caught in the classic trap which faces all those teams that approach the spring with hopes alive on all fronts. Barcelona may be able to coast along in Spain, while in Germany Bayern Munich are also capable of clean sweeps while in second gear.
But City are facing a wall assembled by too much football, the lack of a winter break and a fixture list which has suffered a concertina effect as a result of the Euro 2016 finals this summer.
If they are to succeed in the cups and revive their Premier League challenge - Pellegrini's side are only six points adrift of leaders Leicester City with 12 games left - they could end up playing 66 games this season (not including replays), with a schedule of a game every three-and-a-half days.
When Manchester United achieved the Treble in 1999, Sir Alex Ferguson's team played a total of 63 games, having exited the League Cup in December, and Gary Neville admitted that the incessant workload eventually became a motivational factor.
"We relished the looming challenges," Neville claimed in his autobiography, Red. "So much so that Jim Ryan, who had become first-team coach alongside Steve McClaren, started a countdown, as if he was counting the steps to greatness.
"'Twelve to go, boys,' he'd say when we came in after another victory. And then he would knock another one off and it would be 11 to go, 10. Ten games to make history."
City are yet to hit the final straight and already are beginning to show tell-tale signs of wear and tear.
Perhaps the greatest team in the club's history are now facing their last big challenge before Guardiola arrives to call time on the City careers of such players as Yaya Touré, Samir Nasri, Martin Demichelis, Pablo Zabaleta and perhaps even David Silva.
Chelsea could be the make-or-break moment, the game which either inspires a surge or signals the beginning of the end.
So it is all down to the numbers and whether 27 into 98 can really make four.