Mbappe is now starring with PSG, while Gabriel is yet to experience a defeat at City.
Giggs believes there have been serious shortcomings in the club's transfer policy over the years, and it's coming back to bite them now.
Speaking to The Times, Giggs described it as a 'no-brainer' to sign the players.
He said: “I watched Gabriel Jesus play three years ago. I watched [Kylian] Mbappe for a year. I was watching them with the scout and it was a no-brainer.
"It was just like, 'Get them.' It would have been £5 million or something — get them, loan them back — and that's where the recruitment could have been better."