Pep Guardiola will have one or two things to ponder following his side's defeat against Chelsea, and he will have several players looking to help him out against Celtic. On the face of it, there is very little riding on Tuesday night's Champions League game between Manchester City and Celtic. City are already through to the last 16 of the competition as runners-up in their group, meaning they cannot leap frog Barcelona into first place no matter what happens at the Etihad Stadium or elsewhere. Celtic, similarly, are bottom of the group and cannot claim a Europa League place even if they can mastermind a victory.

It means Pep Guardiola will make a number of changes to his line-up for the game, which may not appeal to many neutrals deciding which game to watch on TV. But given recent events, particularly in the 3-1 defeat to Chelsea at the weekend, there is more riding on this game for City than it may seem. City certainly created enough chances to win the game and Guardiola is pleased with his team's performance, but his side's late red cards, if nothing else, will give him something to think about.

Here are five areas of concern and five players who can do something about it - starting on Tuesday.

 

GOALKEEPER JITTERS - WILLY CABALLERO

When things have gone wrong for City this season, Claudio Bravo has often found himself in the firing line. The Chilean gets more criticism than he deserves - in some cases merely because he is not Joe Hart. The nerves felt when he has the ball at his feet stem more from the fact English football observers are not used to his style of goalkeeping than anything else, because his passing is by far the strongest area of his game and he very rarely gets it wrong. But that said, there is a concern that he is a contributing factor to City's lack of clean sheets. Bravo could surely have done better for Chelsea's second goal on Saturday, and while there have not been any glaring handling errors that have led to goals since the wobble on his debut at Old Trafford, there is a feeling he isn't saving enough of the shots that come his way.

Caballero played against Barcelona in City's most recent European home clash and acquitted himself well. It goes to show how lowly Bravo is considered by some fans (again, sometimes unfairly) that Caballero would now be their preferred choice, given how uncertain the Argentine has made supporters feel during his time at the club. Guardiola has often praised Bravo's ability to shake off any mis-steps with his passing - given it plays such a huge part in City's gameplan - but with the Blues not scoring their chances, they will need to rely on somebody to keep the ball out of their own net. If Caballero demonstrates an improvement in his kicking and reading of the game, he could make a case for a more regular role.

 

DEFENSIVE FRAILTY - TOSIN ADARABIOYO

Guardiola does not make a distinction between defending and attacking but what is clear to see is that his attackers are better players than his defenders. The Catalan wanted to shake up the full-back position and sign two centre-backs during the summer but only ended up with one new centre-back, meaning he is keeping his eye on the transfer market. Vincent Kompany's persisent injury problems mean Guardiola has been robbed of one option for most of the season, while Nicolas Otamendi has struggled in many games.  Aleksandar Kolarov has been the full-back most called upon when Guardiola has switched to a back three but he has been poor on several occasions, and his lack of pace was exposed against Chelsea in particular. There are also no plans to keep Pablo Zabaleta, Gael Clichy and Bacary Sagna beyond the end of their contracts this summer. So talk has now turned to City signing a defender in January but club officials had ruled out that possibility as recently as the end of November.

That may have changed given Kompany's latest injury but one man who could establish himself over the next six or seven months is Tosin Adarabioyo. The 19-year-old is training with the senior squad on a full-time basis but has only played 30 minutes of first-team football this season, and that was against Steaua Bucharest in the Champions League play-off second leg. With City light on defensive options, and light on potential reinforcements in January, Adarabioyo could get a chance to show what he can do. Tuesday night could provide a great starting point.

FERNANDINHO'S BAN & TOURE'S ARREST - FERNANDO

Fernandinho has been a key member of Guardiola's City project but he will miss the next four games (one in Europe, three in the Premier League), meaning somebody will be needed to pull the strings in the middle. Fernando has only tended to be selected when City need a more robust presence in the midfield, and is by no means a shoe-in to replace his countryman. Ilkay Gundogan was signed to play in Fernandinho's position and could now be moved further back in midfield, opening up a more advanced role.

But with Yaya Toure not in contention for European games, and due to appear in court on a drink-driving charge which will do little to impress Guardiola, Fernando can stake a claim for a place at the heart of City team in the coming weeks, with Gundogan deployed closer to the opposition goal.

LACK OF PACE ON WINGS - LEROY SANE

This is more of an individual issue than a collective one. Sane has only shown brief flashes of his ability since signing for City for an initial £37 million this summer, but was selected to start against Chelsea at the weekend. He had a quiet start but grew into the match and, after the break, almost created a second goal for his side with a blistering run from inside his own half. But he tired and was withdrawn well before the end.

Guardiola has come to rely on wingers in recent years and Sane will be expected to play a much bigger role in the coming months as he settles into life in England. The 20-year-old will surely start against Celtic on Tuesday and has a great opportunity to show off his talents in a low pressure environment.

AGUERO'S BAN - KELECHI IHEANACHO

Guardiola will need a replacement for Aguero, who is ruled out until December 31 through suspension. Iheanacho stood in for the Argentine earlier this season, scoring twice in three games, and looked right at home in the City attack. But things appear a little different now, given the Nigerian has not featured as much as expected in recent weeks. Guardiola insisted at the start of the season that he would rotate Aguero in and out of the team in a bid to keep him injury free, but that has not really been the case. Iheanacho has played just seven minutes in the Champions League this season - during that run when he filled in for Aguero in September, where he actually scored - and in the last five Premier League games he has played just 13 minutes.

Even with Aguero now out of the picture for the next four domestic games, there is no certainty that Iheanacho will be first choice replacement, so a lot could ride on his performance against Celtic. And with Gabriel Jesus, the highly rated 19-year-old Brazil international, arriving in January, Iheanacho will have even more competition very soon.