Supporters returned to English top-flight matches for the first time since March on Saturday.
England's coronavirus restrictions have seen fans banned from sporting venues until now.
On Saturday, West Ham became the first to host a top-flight match with spectators present in their clash with Manchester United in East London.
Government restrictions mean just 2,000 fans were allowed to watch the match at the London Stadium, which Manchester United 3-1 thanks to goals from Paul Pogba, Mason Greenwood and Marcus Rashford.
West Ham v Manchester United ratings
Chelsea's game against Leeds United at Stamford Bridge in West London also had 2,000 fans present.
It was the first time Chelsea fans had seen their team play live in nine months due to Covid-19 restrictions, and those in attendance went home happy as the Blues came from behind to secure a 3-1 victory to go top of the Premier League.
Asked if Chelsea fans are right to consider them title contenders, Lampard told reporters: "There's certainly nothing wrong with the fans thinking that.
"It's great to have them back, their input was huge, the noise huge. You can see how excited they are at the end that we are top of the league," he said.
Chelsea v Leeds ratings
The English Football Association has condemned fans of London second-tier club Millwall for booing as players from their team and visitors Derby County took a knee before their Championship match on Saturday.
The game was among the first matches to see a return of supporters to stadiums since the start of Britain's Covid restrictions in March.
Players throughout English football have been taking a knee since July, initially in support of the Black Lives Matter movement, although both the Premier League and the Football League (EFL) have since said the gesture is now linked to their own anti-racism campaigns.
Video footage of the start of the game contained loud booing from the 2,000 fans inside Millwall's The Den stadium as the players took the knee.
In response, the FA said in a statement: "The FA supports all players and staff that wish to take a stand against discrimination in a respectful manner, which includes taking of the knee, and strongly condemns the behaviours of any spectators that actively voice their opposition to such activities."
On Friday, Millwall players had released a statement saying:
"As a squad we are fully supportive of the entire football family’s efforts in ridding the sport, and society generally, of all forms of discrimination.
"The gesture of taking the knee before matches provides an opportunity for us to do exactly that and continues to allow all those playing to publicly showcase their support – on behalf of the whole squad – for the fight against discrimination," read the statement.
“We wish to make clear that taking the knee, for us, is in no way representative of any agreement with political messaging or ideology. It is purely about tackling discrimination, as has been the case throughout.
“We will continue to do this until the start of the New Year when a new and comprehensive anti-discrimination strategy will be announced by the club.”