Manchester City are among the elite European teams investigating the possibility of making arguably the biggest signing of all time in Lionel Messi, but there is one question it seems almost sacrilegious to ask...

Is Messi - as he is now - actually worth breaking the bank for?

The Argentine, who has told Barcelona he wants to leave, is undoubtedly one of the greatest players ever - perhaps even the best - and one of the most successful too.

And while the 33-year-old was the top scorer in La Liga last season, it was still his worst campaign for goals and appearances since 2007-08.

And yet, a record-breaking season for assists tells another story entirely.

So BBC Sport examines whether Messi is in decline - or if he is still the greatest player in the world.

Show us your medals
Lionel Messi has won the Ballon d'Or six times - one more than Cristiano Ronaldo. Nobody else has won more than three

The reason it seems remiss to ask whether Messi is worth signing for a fortune is because of what he has done in his career.

Messi has won more Ballon d'Or awards - given to the best player in the world - than anybody else, with six. That includes the most recent one in December 2019.

He is Barcelona's all-time top scorer with 634 goals in 731 games, and La Liga's record goalscorer with 444 in 485 appearances.

His personal peak was probably in 2012 when he scored 91 goals for Barcelona and Argentina in 69 games.

He has 34 club honours, including 10 La Liga titles and four Champions Leagues.

On top of that he is Argentina's record scorer with 70 goals in 138 international games.

"He is simply the greatest to have ever played the game," said former Barcelona striker Gary Lineker in a BBC Sport column in May.

"An extraordinary combination of things makes him a complete one-off. Messi is also right up there with Diego Maradona as the best dribbler there has been. On top of that, he's also quite possibly the best passer of the ball we have ever seen."

Is he still the best goalscorer in the world?
Messi might not be quite as good as he used to be, but his performances last season were enough to show he is still the best attacking player in the world - by far," said Spanish football journalist Andy West, who has written a book on Messi.

But on goals alone, he is not the best any more.

Messi won a record seventh Pichichi (La Liga's 'golden boot') - his fourth in a row - with 25 goals, four clear of Real Madrid striker Karim Benzema.

That was despite playing in the worst Barcelona team in years, the first to finish without a trophy since 2013-14.

It was the first time La Liga's top scorer managed fewer than 30 goals since Mallorca's Dani Guiza 12 years ago. Deportivo la Coruna's Diego Tristan, in 2001-02, was the last player to win it with fewer goals than Messi.

Yet he still made two bits of history (three including becoming the first player to win seven Pichichis).

Messi broke Xavi's record for assists (20, 2008-09) in a La Liga season by setting up 21 goals.

He also became the first player to score and assist 20 goals or more in a La Liga season. The last player to do that in Europe's top five leagues was Thierry Henry at Arsenal (24 goals, 20 assists in 2002-03).

Of all the players in Europe's top five leagues (in all competitions) Messi was only the joint-sixth top scorer - with 31 goals in 44 games (0.7 goals per game).

Bayern Munich's Robert Lewandowski scored 55, with Serie A trio Ciro Immobile, Cristiano Ronaldo and Romelu Lukaku as well as RB Leipzig striker Timo Werner, now at Chelsea, all scoring more than Messi. Manchester City's Raheem Sterling also scored 31 goals in all competitions.

But when you factor in assists too - 25 in all competitions - Messi shoots up to second with a combined 56 goal involvements.

So is Messi still the best?
There is still a strong argument to say Messi is one of the very best players in the world, although Lewandowski probably had a better 2019-20 season than anybody else.

He is one of the best goalscorers in the world, one of the best dribblers and one of the top passers.

There is also a strong argument that he could do even better in a strong team, with Barcelona looking ragged at stages last season even before their 8-2 season-ending thrashing by Bayern Munich in the Champions League, which looks like it may be Messi's last game for the club.

He won the La Liga 'golden boot' and was involved in more goals than anybody else bar Lewandowski last season, so would clearly still be a huge asset for any team.

The only thing not on his side is time, although former Barca team-mate Xavi recently said he thinks Messi could play until he is 40.

MOTD host Lineker said: "It has been an absolute privilege to watch Messi and his last game will be one of the saddest days in football history.

"No footballer can last forever and you can start to see that his powers are waning a little bit. It doesn't matter how good a player you are - you cannot beat Father Time."

West said: "Messi is still the best, and he will be for a few more years yet."

So what do you think? Is 33-year-old Messi worth buying at all costs?