5 Truths: Lionel Messi is unstoppable, Theo Walcott really is good now

The look on Pep Guardiola's face at full-time said it all. It was a thoroughly miserable return to the Camp Nou for the Spaniard, and one man was behind the destruction: Lionel Messi.

Two of Messi's three goals were scored after Manchester City had been reduced to 10 men as a result of Claudio Bravo's reckless handball, but that point does not reflect the ease at which Barcelona and their star forward were running rampant even prior to that point.

Put simply, Messi was totally unstoppable and Guardiola knew it. His City team were unable to cope with the quality of Barcelona's forward play and Messi was able to run riot at the expense of his former coach.

When Pep Guardiola decided to confine Sergio Aguero to the bench for the visit to the Camp Nou, it's fair to say that eyebrows were raised. However, this is the Spanish master, so we should trust him no matter how bonkers his ideas are, right?

Well, as City sat further and further back without a creative spark in attack or a threat in the final third, the game looked increasingly hopeless for the Premier League side - something which was pretty avoidable. With the exception of Claudio Bravo's crazy decision-making, that is.

Yes, Barcelona deserve respect; and yes, it is foolhardy to believe that you can always play the same way; but Guardiola did not give his side a chance to perform as they were potentially capable of, because of his negative approach.

Let's take nothing away from Arsene Wenger's dominant side after their emphatic victory over Ludogorets. Well, actually, let's take something very minor away by stating that this thrashing was simply a case of disposing of wildly inferior opposition at home.

Mesut Ozil, Theo Walcott and Alexis Sanchez were utterly rampant in handing Wenger his 100th victory in Europe, but no one should get at all carried away by a convincing win against pretty hopeless opponents.

Arsenal are on fire right now and Wenger's men look incredibly impressive in racking up victories, but we have seen all of this before. Yes, it was a fine win, but Barcelona and Real Madrid are still on another level entirely.

It still feels strange to say it, but Theo Walcott really does seem to be the real deal right now. The Englishman has now scored six goals in his last four games at the Emirates and three in the Champions League already this campaign.

He may not have found a satisfactory level of consistency in the past, but he does appear to have assumed a new standing within this Arsenal side and the results are really starting to bear fruit.

Seven goals in his last six appearances demonstrate that Walcott has found a consistency in his production; now, can he maintain this level of play until the end of the season? If so, he was worth persevering with for the ever-patient Wenger.

It all started pretty brightly for Brendan Rodgers' Celtic team in the Champions League this season. As Rodgers himself pointed out, other than the early goal conceded against Barcelona they had a decent opening spell and even had a spot kick… which they missed. "We had a massive moment in the first half. We went 1-0 down very early but we had a great chance to level the game [from the penalty spot]. If you get a penalty and get the score to 1-1, it makes it a little nervy — especially after them losing here at the weekend."

Sadly for Brendan and his men, Barcelona went on to knock another six goals in that night – a result which looks much less humbling in the light of Manchester City's 4-0 defeat – but they continued to scrap, and the thrilling 3-3 draw with City a few weeks later was one of the most exciting European nights Glasgow has seen for years.

But that's that. They might as well shut up shop now. Celtic were hopelessly outplayed by Borussia Mönchengladbach, a team most of Celtic's supporters couldn't spell before 7.45pm on Wednesday night.

The end result? A 2-0 defeat, a -9 goal difference, and a single point from three matches… with away clashes at the Etihad Stadium and in Germany to follow, as well as another game against Barca. Even a spot in the Europa League seems hopelessly unlikely now.

Rodgers was brought in to change things up for Celtic in Europe. Only a 'Miracle in Mönchengladbach' on November 1 will stop that mission from being declared a total failure.