Barca had announced an agreement had been reached with the Argentina international in July, but the lack of a signature and the customary photograph with the president had not materialised, leading to speculation he would be able to negotiate with other clubs as of January, with his previous terms due to expire next summer.

Here are five reasons why it was so important that the Catalan club got Messi to commit.

1. The situation was becoming a sideshow

No one doubted the agreement the club announced in July, but as the months passed, the lack of Messi's signature became stranger and stranger. Why had he not signed?

It got to the point where every time someone from the club spoke publicly, they were asked about Messi. This week alone, Ernesto Valverde, Ivan Rakitic and Denis Suarez were all questioned about his future.

On Friday, Messi had the perfect chance to clear things up when he spoke briefly after being awarded the European Golden Shoe. But he turned down that opportunity.

Marca director Juan Ignacio Gallardo, who was doing an introduction at the event, immediately shot down any potential questions, saying, "It's not the day to speak about his future."

That raised even more doubts. Therefore, it was important that Barca stopped this from getting out of hand as another Neymar situation threatened. That's why Saturday's signing and photograph had become necessary.

2. Barca keep one of the game's greats

Just where Messi features on the pyramid of football greats is still up for debate. What's not up for discussion, however, is that he's near the very top.

The list of honours he's won as a Barcelona player -- individually and collectively -- is extensive and includes eight La Liga titles, four Champions Leagues and five Ballon d'Ors.

Along with Cristiano Ronaldo, he's also taken the art of goal scoring to a new level. In just over 600 appearances for Barca, he has scored 523 goals. Last season he scored 54, and he already has 16 this year in all competitions.

It should go without saying, then, that Barca simply could not afford to lose one of the best players to ever play the game.

3. Confirms Messi's commitment

Messi has always said, with the exception of, perhaps, a spell at Newell's Old Boys when he's older, that he wants to end his career at Barcelona.

That has never really been in doubt, but as the contract saga dragged on and we moved toward January, when he would have been able to negotiate with other clubs, there were more than a few legitimate questions.

However, those questions are no longer relevant. Messi, true to his word, has committed his future to the club where he has spent more than half of his life.

"I have always wanted to spend my whole career here," he said after signing the deal. "My dream is to end [my career] at Barcelona, and I am on the path to doing that."

Lionel Messi celebrates after opening the scoring for Barcelona against Athletic Bilbao. Getty Images

4. Attracts other players

Players sign for Barcelona because they want to play alongside Messi. With him gone, some -- not all -- would have found the club a less attractive proposition.

But with Messi in place until 2021, it's a sign that Barca are not going to miss out in the transfer market anytime soon. President Josep Maria Bartomeu labelled Messi "the best player in the history of the game" on Saturday, and it gives the club a great bargaining chip to strengthen their squad.

5. A new buyout clause

One of the reasons there was a delay in finally signing this new contract was because an important adjustment was needed. The new terms Barca announced in July included a €300 million buyout clause. The contract signed by the forward this weekend featured one now worth a staggering €700m.

The reason for the increase was because of the panic generated at the club by Paris Saint-Germain's capacity to pay €222m for Neymar in August and the changing football landscape.

"In June, we agreed a contract with Lionel Messi, which is already operative, but we've had to make some changes simply to make the buyout clause more adequate for the current football market," Bartomeu explained. "That is now €700m, which situates Messi where he should be."

Even PSG or Manchester City are unlikely to be able to pay that sort of money without breaching UEFA's Financial Fair Play rules, so it looks like Messi will be at Barca until his mid-30s, at least.

If the club get their way, though, he will be there for good. CEO Oscar Grau has already said they're planning a lifetime contract for him, similar to the one signed by Andres Iniesta earlier this year.