After Sunday's 0-0 draw at Crystal Palace, when only a penalty save by goalkeeper Ederson in stoppage time saved Pep Guardiola's team from a first Premier League defeat of the season, will City get the show back on the road by starting another winning run by defeating Watford at the Etihad on Tuesday?

Or are we seeing the first cracks in the City facade -- cracks which might just offer a glimmer of hope to Chelsea in their attempts to defend the title they won so convincingly last season?

While all eyes have been on Manchester United's increasingly unconvincing efforts to keep pace with City at the top of the table, Chelsea have embarked on a run of 10 wins from their last 13 league games, losing just once, and their return to form has largely gone unnoticed.

In any other season, such a sequence of results would have propelled Chelsea to the top of the pile, but City have raised the bar to a completely new level this season, which is why their failure to win at Selhurst Park was such a surprise.

City's inability to extend their 18-game winning run against a team battling to avoid relegation should give the rest of the league hope, and ensure that future opponents try to beat Guardiola's men -- as Roy Hodgson's team attempted to do -- rather than adopt the negative, and fruitless, safety-first approach taken by Newcastle at St James' Park last Wednesday.

But if Sunday's draw at Palace was the first sign of a City wobble, the demands of a testing January will tell us whether it is enough to knock them off their stride or merely prove to be nothing more than a brief stumble on their march to record-breaking glory.

First of all, Guardiola's squad is beginning to suffer from injuries and the absences of key players.

Vincent Kompany limped out of the 1-0 win at Newcastle with his latest injury setback, while Gabriel Jesus and Kevin De Bruyne both failed to finish the game against Palace. Jesus faces up to two months out with suspected knee ligament damage, while De Bruyne's injury, not believed to be as serious as his teammate's, will almost certainly force the Belgian to miss the Watford game.

On top of the injuries, David Silva has played just one of City's last five games due to personal reasons.

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The injury to Jesus could prompt City to bring forward plans to sign Alexis Sanchez from Arsenal, with the current necessity for firepower likely to outweigh the determination to wait until the summer to sign the Chilean on a free transfer.

Needs must and, with Sanchez eligible to play in the Champions League, it seems inconceivable that City will now not make an attempt to sign him this month.

Sanchez will only make City stronger and more formidable, but Guardiola has already highlighted the physical demands of playing up to eight games in January, so even the addition of the Arsenal forward may not be enough to stave off a difficult month.

Watford is the first test, with Marco Silva's team going into the game having had almost 24 hours extra rest than City since their defeat against Swansea on Saturday.

There are then FA Cup and Carabao Cup ties against Burnley and Bristol City respectively before City travel to Liverpool on Jan. 14.

City have lost their last four league games at Anfield and have not claimed three points away to Liverpool since May 2003, so if any fixture is likely to trip them up and end their unbeaten record, it is that one.

Guardiola's team have already passed many tests this season, but it is now that their endurance will be questioned.

Once injuries begin to drain the squad, fatigue can set in among those players left standing, with the physical toll truly beginning to tell in April and May, when batteries begin to run on empty. But by then, with a 14-point lead going into 2018, City should have the Premier League title all wrapped up.

United allowed a 14-point lead in December 1993 to be completely erased by Blackburn by April 1994, but the Old Trafford outfit recovered to win the title that season regardless and City now have such a cushion that it would take a huge collapse, and a long winning run by Chelsea or United, for them to finish anywhere but top.

Yet after being so impressive for so long, the draw at Crystal Palace offered proof that City can be stopped.

If the injuries fail to clear quickly and if Liverpool get a result against them in two weeks' time, City might just stumble.

It is all "ifs" right now, but the chasing pack did not even have those to cling to before the Crystal Palace game.