Mane, who left Liverpool for Bayern Munich in the summer, is one of the most high-profile absentees from this winter’s tournament in Qatar.
A calf injury suffered in Bayern’s 6-1 win over Werder Bremen, their penultimate game before the break, required surgery and has seen the 30-year-old ruled out for the duration.
Senegal have progressed to the last 16 without their talisman, though, and face England in a knockout clash on Sunday evening.
Speaking to talkSPORT ahead of that tie, Alexander-Arnold said he was “absolutely gutted” for his former team-mate, but admitted it “probably helps” England’s chances.
“Sadio brings a completely different aspect to that side,” the right-back said.
“[He was] one of the top, might have got top three in the Ballon d’Or this year, or top five at least anyway. That’s all that needs to be said, really.
“A world, world-class player. As bad as it sounds, it probably helps us that we’re not playing against him.
“That’s the level of player.
“I only say that out of pure respect for him, because I’ve played against him in training and it’s not a nice feeling.
“He’s one of, if not the, best left wingers in the world in my opinion, and someone who can win games. I’ve seen it on multiple occasions and I’ve been a part of a team that has benefited from it.
“I was absolutely gutted that he had to miss out on this tournament. He’s someone who I’ve got a really good relationship with.”
Alexander-Arnold is not likely to start in the meeting in Al Khor, having made his only appearance of the World Cup so far off the bench in the 3-0 win over Wales on Tuesday.
He will be a captivated onlooker, though, with the Three Lions needing to be “at 100 percent” in order to progress to the next stage.
“They’re a top team. I think any team that reaches the last 16 is going to be a top team,” he said of Senegal.
“I’m sure, no matter what we say or what we do, we’ll be going into the game as ‘favourites’, the media will paint that.
“But we, as a team, understand how good they are and understand that in 90 minutes of football, anything can happen.
“If we play at 90, 95 percent, then we’ll be going home, because that’s not good enough. If we’re not at 100 percent, then it’s not good enough at all. That’s where our heads [are] at.”