Barely a minute was enough time for him to get on the scoreboard in his second outing.
Saibari drilled a shot into the top corner of the net a mere 72 seconds into Friday's 1-0 win over Scotland at Gillette Stadium, keeping alive Morocco's chances of advancing to their second straight World Cup knockout round.
"We wanted three points and we got them," Morocco coach Mohamed Ouahbi said.
Morocco's ball movement caught Scotland on their heels at the very start.
Saibari slipped behind two Scotland defenders and Brahim Diaz dropped the ball over the top to him. The 25-year-old forward gathered and blasted it into the top left corner, well outside the reach of goalkeeper Angus Gunn.
Morocco, who reached the semifinals at the last World Cup in Qatar, drew 1-1 with Brazil in their Group C opener with Saibari scoring the lone goal.
Scotland, who haven't gotten out of the group stage in their eight previous World Cup appearances, beat Haiti 1-0 in their first match.
Scotland were outshot 12-6 on Friday, struggling to get clear looks against Morocco's defence.
But the negative result didn't affect Scotland coach Steve Clarke's confidence in his team.
"We gave them a game," Clarke said. "We're sure we can compete at this level."
Morocco nearly scored another in the 52nd minute when a header by Bilal El Khannouss off Achraf Hakimi's corner kick was batted down by Gunn.
Scotland had a chance in first-half stoppage time when Andy Robertson sent a cross at John McGinn, who couldn't get a foot on it near the back post.
As Scotland pressed for an equalising goal in the closing minutes, Morocco had a pair of good chances to add to their lead, but both missed the target.
"I thought the performance didn't match the result, if I'm honest," Scotland midfielder Lewis Ferguson said. "We took the game to them. So there are positives from both games that certainly we can take into this last game."
Scotland will face Brazil in their final Group C match on Wednesday in Miami Gardens, while Morocco take on Haiti at the same time in Atlanta.