The Belgium worldwide suffered an injury in training on Wednesday and will be out for three months.
"Kevin is a great player and it's just unfortunate that it's happened to him in training but there's more than enough depth in the squad", City right-back Kyle Walker said on Wednesday evening.
"This can happen because you build an awesome stadium for Tottenham Hotspur - sometimes there are delays, this kind of thing happens".
De Bruyne was City's player of the season last term, scoring 12 goals and providing 21 assists as his side won the Premier League and EFL Cup.
"We'll never know but my opinion is that we demand a lot of the players", he added. It's a tough season, short recovery, they say let's go and we are in the competition. "If you're fresh, with normal vacations, then that doesn't happen".
David Silva, who this week announced his worldwide retirement, missed the Arsenal match and the Community Shield victory over Chelsea with a knee injury and could be back to face Huddersfield at the Etihad Stadium.
Speaking in an interview with Sky Sports, Smith said: "I do not think it will be a particularly entertaining campaign for United fans, but they had a great defensive record last season and although he did not get his centre-half, there is no reason why they will not be as hard to beat".
"My advice to him now is to rest, take the holidays he didn't get in these two or three weeks, do it now".
Kevin De Bruyne's knee injury is a major disappointment. "Big congratulations because he played more than 100 games, winning European Championship and the World Cup. He made a decision to rest a little bit more with his wife and his little boy, and play with us".
City had the chance to claim the Premier League title against their cross-town rivals United in April.