Musettti collected the four aces of the match; He settled the duel between 23 -year -old players in an hour and a half.
Musetti dominated 4-1 for the breakage and it was limited to 12 direct faults, against 37 for the Canadian.
Ranked 78th in the world, Diallo was a medium to the net (11 in 24), facing a rival which was 3 in 5 in this aspect.
Musetti will have as a rival in the semi-finals Jack Draper, from England.
Draper has the advantage 3-0 in their confrontations.
The only breakage succeeded by Diallo gave him the lead 4-2 in the first set.
The Italian, however, played the same turn to him on his following two occasions, including a game to zero to lead 5-4. He won the game when Diallo sent an off -target smash.
In the second set, Musetti kept the course after a breakage placing him in the orders 2-1.
-Diallo committed four direct faults in the last game, including an Smash in the net at 15-15.
Musetti prevailed at his first match ball, on a head -to -the -day target of the Quebec player.
During the second Canadian bullets, Musetti scored the point 20 times out of 26.
It was for Diallo a first presence in the quarterfinals in Masters 1000.
His outfit in Spain should bring him a place in the TOP 60 of ATP.
Next week, Diallo is scheduled to take part in Italian omnium in Rome.
Musetti is already assured of a first breakthrough in the top 10 in career.
It is nine gains since 10 outings. The only setback was against Carlos Alcaraz, in the final in Monte Carlo.
