McManus, 43, had not won a match at the World Championships since he beat Ken Doherty in the last 16 in 2005, but he will now face the 44-year-old, another former Crucible winner, at the same stage on Friday.
He secured that appointment with Doherty by beating his long-time friend Higgins in a tight battle on Tuesday, snuffing out the Wishaw man's mini-revival in the second session to complete a 10-7 victory.
The Glaswegian they call Angles - for his precise style of play - believes that younger players should start following the example of the old guard to prolong their careers at the very highest level of the game.
"I think there's still plenty of room for guys over 40, 42 - whatever it is - to compete at the higher level of the game," said the world No.35. "I also think the older players have stolen a march on today's young brigade. Today's world isn't good for young people in snooker terms because they spend all their time on Facebook and it's killing their snooker.
"I've seen it, they're too busy reading and writing about snooker instead of getting their nut down. I'm on Twitter but don't post messages very often: only for fun. It's just my personal opinion. Not all of them do it but some of them are spending too much time on the internet."
Of Friday's prospects, he said: "I'm pleased for Ken; we play a similar type of game. I've always enjoyed watching him and he did really well in qualifying last week; we've had similar stories coming through [qualifying ties]. I remember the last time I played Ken here; I think it was 13-11. It was a really good match; hopefully we'll have something similar."
Higgins had won the last three frames in the first session to head into yesterday's second session with the momentum, but poor positional play initially blighted his comeback attempt and his position looked hopeless as he fell 9-4 adrift.
However, the world No.9 rallied to pull it back to 9-7 - he had a match-high break of 111 - before missing a crucial blue in the 17th frame to open the way for McManus to triumph.
"I scraped over the line in the end; I said to my pal at the break that John's going to come on strong here; it's what he does," added McManus. "It was no surprise, if John starts relaxing and putting his arm through the white the way he can do it's like trying to tame a lion at times. Any time for me to even practise with John is just a thrill frankly. I hold him in such high esteem as a guy and a player; he's a legend of the sport."
Higgins, the 38-year-old former winner, has struggled to find his best form since his last World Championship success in 2011 but, while he admits he may never reach those heady heights again, he is adamant there is plenty left in the tank.
"There have been times I've sat here desolate, thinking there's nothing at the end of the tunnel but I definitely think I've got some decent snooker left in me," he said. "I might not be one of the top players you think of challenging for every event - I'm possibly a journeyman top-16 player now - but every journeyman can have his day sometimes."
Of the finish, he said: "I had to play [the last blue] really thin because I knew it would have cannoned into the brown, and I just took my eye off it. Alan then cleared up and it was disappointing the way it finished because I was playing pretty well."
Higgins refused to rule out his fellow-countryman against Doherty either. "Alan played three matches just last week and has Ken next - that's going to be a battle and they've had great battles. I've got a lot of respect for Alan and people such as Stephen [Hendry] because if it hadn't been for practising with them when I was younger I wouldn't have become the player I am today."