The Blues wrapped up a £71million deal for Havertz earlier in the month, with the German midfielder signing a five-year deal at Stamford Bridge.
Havertz, 21, scored 36 goals and made 25 assists in 118 appearances for Bayer Leverkusen and will be a ‘massive player’ for Frank Lampard, according to Cascarino.
The ex-Chelsea and Republic of Ireland striker even says Havertz is a better signing than Sancho, who continues to be linked with a move to Manchester United.
Sancho has developed into one of the most exciting and coveted players in Europe since joining Borussia Dortmund in 2017 and United are weighing up a £100m offer for the England star.
Havertz has been joined at Stamford Bridge by fellow Germany international Timo Werner, Moroccan star Hakim Ziyech, England defender Ben Chilwell and Brazilian veteran Thiago Silva.
Discussing Havertz and Chelsea’s summer signings, Cascarino told The Times: ‘I cannot wait to see Kai Havertz, Timo Werner and Christian Pulisic leading the line for Chelsea.
‘Frank Lampard’s team now have the most exciting front three in the Premier League and, whisper it, they have what it takes to be more prolific than Mohamed Salah, Sadio Mane and Roberto Firmino at Liverpool.
‘Pulisic and Havertz are blessed with pace and great technique, and Werner is a lethal finisher.
‘Havertz, in particular, is going to be a massive player for Chelsea. He is a better acquisition this summer than Jadon Sancho would be.’
Following his move to Stamford Bridge, Havertz said: ‘I am very happy and proud to be here. It is a dream come true to play in a big club like Chelsea.’
Chelsea begin their 2020-21 Premier League campaign on Monday evening with a trip to Brighton.
The Blues finished fourth in the top-flight last term and reached the FA Cup final.
For more stories like this, check our sport page.