Gundogan, who returned from a nine-month injury lay-off in September, grabbed a brace as City now have one foot in the quarter-finals.
In-form Sergio Aguero scored his 198th City goal and Bernardo Silva also got on the scoresheet as Guardiola’s side cruised to victory on a freezing night at St Jakob-Park, but it was Gundogan who was rightly singled out for praise after the game.
“Ilkay Gundogan is an extraordinary player. Last season we missed him a lot with injury for six months and that’s why we are so satisfied, not just the quality but personality to play,” Guardiola told BT Sport.
Despite being in complete control of the last 16 tie, Guardiola says City will remain focused ahead of the second leg at the Etihad Stadium.
“An excellent result,” Guardiola added. “We are almost in the quarter-finals. Champions League is always 180 minutes and we will take the game seriously but it’s an excellent result.
“We are still in February and in the Premier League we are in an amazing position and we are almost in the quarter-finals, we are in one final (Carabao Cup) and on Monday we have the opportunity to reach the quarter-finals of the FA Cup.”
Uwe Rosler was sacked by Fleetwood following a 3-0 reverse at Doncaster which condemned Town to a seventh straight defeat in all competitions.
Cambridge interim head coach Joe Dunne was pleased with how his side adapted to beat Grimsby 3-1.