Messi
Messi has already scored 97 goals in the Champions League. Getty

Barcelona manager Ernesto Valverde has no idea whether Lionel Messi took a glucose tablet before scoring his 100th European goal during the Catalans' 3-1 victory over Olympiacos in the Champions League on Wednesday night (18 October).

The five-time Ballon d'Or winner also set up Lucas Digne's third goal of the game as the La Liga giants consolidated their position in Group D, sitting three points ahead of Juventus after winning their opening three games.

Messi also attracted the attention of the supporters in the 10th minute of the game after the Argentine appeared to take something from his sock and put it in his mouth.

Catalunya Radio resolved the mystery by suggesting that the Barcelona ace was only taking a glucose tablet.

It is usual for footballers to take glucose before the games and at half-time, but journalist Ricard Torquemada said that Messi opted to take it midway through the first half as it is when the muscles are most receptive.

But asked about the matter in the post-match press conference a surprised Valverde laughed and joked: "I don't know. If he has took a glucose tablet? I don't know. If it made him score a goal, then he should take a load of them..."

"I have no idea but players do take glucose at half-time. But taking into account that he later scored his 100th goal [in European competition] maybe we have to establish it [as a rule]."

The Champions League win over Olympiacos also saw Messi scoring a free-kick to become the second player, after Real Madrid nemesis Cristiano Ronaldo, to reach 100 goals in European competition.

The Barcelona star has netted 97 goals in the Champions League in 118 matches and scored three goals from four matches in the European Super Cup.

Valverde also joked about Messi's records while challenging the Barcelona to score further 100 before the end of the current campaign.

"I hope he reaches 200 goals this season," Valverde said. "His numbers validate what we see every day, he's beating statistics that seemed impossible. He's been doing it for a long time now, constantly breaking down barriers."