Heskey's old club outclassed United 0-3 at Old Trafford, with Luis Diaz scoring twice before the break ahead of Mohamed Salah taking the game away from hosts soon after halftime.
Speaking to Tribalfootball.com, Heskey admits he was impressed by how clinical Liverpool were on the day.
He said, “The biggest thing in the games these two teams have played over the last few years is taking chances. if you don't take your chances, you inevitably will give the opposition a chance to go and win that game, just like we saw last season in the FA Cup.
“I was at that game, and I thought Liverpool could have been three or four goals to the good, but they missed countless chances and Manchester United ended up going on the break, scoring two and you lose the game and a chance at a trophy.
“However, on Sunday they were ruthless, put United under pressure, forced mistakes, created chances and took them straight away. They took the wind right out of United’s sails because, in reality, despite winning the FA Cup, United as a club are still under pressure.
“Any player will tell you in a local derby or a game of this magnitude which means a lot to the fans, it doesn’t matter what has gone on before, if you can pull off a win, it gives you some breathing space. That is exactly what United did last season, but this year Liverpool just took them to the sword and really finished them off.”
Putting his coach's hat on, Heskey says he can detect changes in the system Arne Slot employs compared to predecessor Jurgen Klopp.
He continued: “I think the dynamics on the ball are a little bit different now because with Jurgen Klopp, especially when he first joined the club, it was all out attack. Let's smother teams, really suffocate the opposition and press them into feeding us chances, which worked really well.
“Whereas now under Arne Slot, it's more of a structured team again, which I think will lead to more consistent performances, especially defensively. Can you do the Jurgen Klopp version for 90 minutes consistently? Liverpool showed over the past few years they could cope with Klopp’s demand and saw plenty of success under him, but it’s a tough way to play football.
“This style of play is more structured with the build-up and trying to create overloads in higher areas of the pitch, recognising the opportunity and fashioning chances for their incredible front line. The first few games of the season look much more controlled than what Liverpool will have become used to over the last few years and it has been working so far.”
Liverpool's big signing of the summer, Fede Chiesa, sat out Sunday, but Heskey says it won't be long before the former Juventus attacker will find his way into Slot's XI.
He added, "I am always excited about any signing that Liverpool bring through the door. I know the club will have done their due diligence on a player who can excel in this system that Arne Slot wants to play. I guess he is cheap when you look at today’s crazy market, but he has had a few injuries and is a little bit older now.
“I think Slot can get the best out of him in the system that they play. It’s been a little bit of a weird transfer window for Liverpool as they have to ensure they comply with financial fair play, but they have a great squad already and Chiesa is a great addition.”
- Emile Heskey was speaking to Tribalfootball.com on behalf of BetMGM