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McTominay, who was named last season's Most Valuable Player in the league, headed Napoli ahead early on before De Bruyne marked his Serie A debut with a goal from a free-kick after the break.

Napoli wasted no time getting started, with De Bruyne registering a shot with just 26 seconds on the clock, and its dominance was soon rewarded in the 17th minute.

Matteo Politano was allowed time on the right-hand side to deliver an inch-perfect cross on to the head of McTominay, who squeezed his effort in at Stefano Turati's near post.

The Scotland international came close to doubling his and Napoli's tally before the break, with Politano's deflected drive striking the post early in the second half.

But Napoli's second came courtesy of De Bruyne, with his free-kick from the left evading the head of McTominay, but nestled into the bottom-right corner in the 57th minute.

Sassuolo's misery was compounded 11 minutes from time when summer signing Ismael Kone was shown a second yellow card for a poor challenge on Lorenzo Lucca.

"We told ourselves we'd start with this mindset, get the three points on a difficult pitch, and that's what matters most," McTominay said after the match.

"It's an honour to have De Bruyne in the team. I'm the one who has to learn from him, not the other way around."

Conte was quick to temper Napoli's Scudetto expectations despite this impressive start to its title defence.

"It will be a very difficult and interesting campaign with seven or eight teams fighting for the Scudetto or Champions League qualification," Conte said.

"We are trying to complete the structure of the squad, and it will require patience."

Conte added he was still waiting to strike the right balance in midfield, after starting with McTominay, De Bruyne, Stanislav Lobotka and Frank Anguissa against Sassuolo.

"I am still trying to find the right formula to ensure the three midfielders from last season can co-exist harmoniously with Kevin," he added.

"We haven't had long to work on it, but I am seeing some interesting things. 

Conte did, however, shower particular praise on McTominay and De Bruyne, with the 56-year-old believing their differing playing styles complement each other.

"Scott is a fighter who can ghost in from deep and become devastating, while he also has a good shot from distance," Conte said.

"The opening goal was a situation we had tried in training.

"De Bruyne has different characteristics, he likes to move it around and rarely runs into the box. We try to ensure all the zones are covered."