A clause in his new contract means the Argentine is consulted on the Blaugrana's transfer dealings.
And according to Don Balon, Messi has agreed that Alcacer is expendable.
Alcacer's style of play has lead Barca to try and find a suitor in the Premier League. However, the 24-year-old is said to prefer a move back to previous club, Valencia.
The Spain international has scored 13 goals in 43 appearances since joining Barca from Los Che in 2016.