Walking into an under-achieving football club is never easy. I know, because I spent my career taking on such challenges.

That was the task Michael Carrick took on in January when he was appointed Manchester United's interim manager and took over a club that was drifting deeper and deeper into mediocrity.

Supporters talk about seeing a bounce when new managers take over and, from my own experiences, I do believe that to be the case.

Michael certainly experienced a fantastic period where results and performances improved. In his case, United's improvement to finish third and in the Champions League places was exceptional - and he also calmed the water behind the scenes.

Yet, with every bounce, there almost always comes a return to normality. You see players who raised the level of their performance return to the level they are used to, and everything often slips back to the way it was before.

That seems to be what is happening at United now but, while Carrick appears to be under increasing pressure, the club's problems are definitely not just down to who their manager is.

Here, I've tried to explain what he needs to do to sort some of his issues out.

To properly judge Michael, you have to balance up everything he has inherited and consider whether United could be a successful organisation.

United have invested enormous amounts of money in recruiting a lot of players in the past five years.

Since 2021, they have had three other permanent managers - Ole Gunnar Solskjaer, Erik ten Hag and Ruben Amorim, who spent more than £1bn on 27 major signings and many of whom are still at the club.

This year, under Michael, they have invested another £150m, but the bulk of it was on three midfielders and if you assess his entire squad I would still seriously question how many players he would have chosen out of the group he now has.

As a manager going into troubled clubs, you have to immediately set your non-negotiable principles with your players - things like hard work and a collective spirit in the dressing room were imperative for me.

You give everyone the same opportunity to jump on board and then quickly recognise the players who are capable of going on the ride with you, and those who can't, or won't.

Michael will know all those things about his squad by now, good and bad, but what can he really do about it?

In my experience, and I am talking about Premier League clubs, my owners were keen on my views on the players I had just inherited - not just in terms of their ability on the pitch but their value as assets on budget sheets and in the transfer market.

I was always continually asked if I could make players better, and also if I could recover money from those I did not rate or want, so as to help the club's financial position.

I understood why - my position as manager was to 100% help the club and try to achieve maximum performances on and off the pitch - but it can be hard to do both.

It means when you are taking over a group of players your club has invested in, you cannot always be completely honest about certain players in that group.

You know the club has a vested interest in holding the player's value and the fact you have to portray positivity to protect that is sometimes unbelievably difficult.

Criticising them in the media can't happen, because of your loyalty to the club, so you are left hoping the people who watch your games week in, week out, understand and recognise your dilemma around your squad.

The club's recruitment strategy has been publicly questioned recently, of course, by defender Lisandro Martinez - and I am sure a lot of supporters agree with him and/or would like some clarity on that subject.

But, from a manager's perspective, Martinez's outburst also raises serious questions about the player himself.

Him saying what he did does make me wonder whether he believes he has been a success personally. If so, then how many more players in United's first-team squad also believe themselves to have been successful, rather than part of the problem?

Managing players with inflated opinions about themselves is another challenge in itself - and it certainly needs addressing.

You can add that to the list of Michael's issues right now, but he has an even bigger problem in how he deals with his captain Bruno Fernandes' comments after United were humbled by Como in the Champions League on Wednesday,

Watching Michael in his post-match press conference in Italy was really difficult for me.

I've managed games where my team has been beaten while having a right go, but having to see a manager man up to his side after a performance that, for me, questioned their attitude to compete or even run around and try, was heart-wrenching.

Listening to the way his captain spoke, after his own example typified his team's reluctance to do the above, it again showed me how difficult it must be at that club at the moment.

Michael's tactics are there to be followed, yet to do that away to Como on a very wet and windy miserable night, you need men and not boys.

Fernandes seemed to be enjoying his relationship with Carrick last season, when United were flying up the table, but they have now levelled off both as a team and individuals in the way I described in this column.

Proper captains, and I was lucky to work with some top guys, come to the fore when the team and club needs them most.

I've always judged leaders by people who follow them when things are going wrong. Unfortunately, many members of that team did follow their captain's example, but in a totally unprofessional way.

I don't know Michael well, but he was a very honest player who deservedly has great standing at the club he is now managing.

I know his backroom staff better - Steve Holland, Jonny Evans and Jonathan Woodgate - and they are all able assistants with knowledge and experience at the very top level.

Whenever United are not winning, there will be calls for things to change - and the manager is almost always at the top of that list.

So, where should they look now? I believe they should follow the blueprint of one of their great rivals, and realise that continuously changing direction is just not working.

When Mikel Arteta arrived at Arsenal in December 2019, he had an instant impact like Michael - not in terms of league position, but by winning the 2020 FA Cup.

For a couple of years after that early success, however, Arteta was taking pelters from fans and across the spectrum of media outlets because the upturn in results did not last.

Despite that, the club never flinched and gave him the opportunity to install a clear identity throughout the club and also time for it to take shape.

Look where they are now.

United have to take their medicine and do similar - they have to understand the consequences of the huge failures in recruitment they have repeatedly made and reset to find a direction and identity again.

Time is their biggest challenge there, because everyone demands instant success these days. People, though, have to realise that, while I believe Michael - when everyone is fit - has a group that can still compete for the Champions League places, they are never good enough for the prizes they really want.

To be contenders again, they need more than just talent. Ability, pace and character are the characteristics they will need in pretty much every outfield position but, from where they are now, achieving that will not happen quickly.

They definitely don't need to change their manager again to get there, however. I was all for Michael getting the job in the first place once Darren Fletcher had been overlooked, and in my humble opinion he should be backed again to do what is needed now.

At this moment, United are not capable of winning the league title, whoever is in charge, but stability is the way forward to fix that.

Tony Pulis was speaking to BBC Sport's Chris Bevan.