Chelsea manager Thomas Tuchel "couldn’t care less" if Romelu Lukaku scores ore goals than Cristiano Ronaldo this season after both new signings netted Premier League doubles.

Lukaku, who joined Chelsea from Internazionale last month, scored the first and third goals in the Blues' 3-0 win over Aston Villa on Saturday.

Meanwhile Ronaldo starred in his second debut for Manchester United, netting a brace as they won 4-1 over Newcastle prompting comparisons between the pair.

"I couldn't care less as long as Lukaku scores for us," Tuchel said when asked who he thinks will score more this season during the post-match news conference.

"Honestly, I know you'd like to have a good answer but unfortunately, I don't have one. Lukaku was decisive for us today and that is what we are looking for.

"He wants to score for Chelsea, help the team with his goals, that is what he did today.

"That is why he is here. He is not shy to speak this ambition out loud because he is full of confidence and is the kind of personality that can handle it. This is what he showed in the first games and today."

Another new Chelsea signing Saul Niguez made his club debut, starting but being replaced at half-time after an underwhelming display.

Tuchel admitted the Spanish midfielder "struggled" but put the blame on himself rather than the player who joined on loan from Atletico Madrid on deadline day.

"He struggled. I take the responsibility for that," Tuchel said.

"I put him into a difficult match after a national break. It was hard for him to adapt to the physicality, and to the intensity and high pressing of Aston Villa. It was also a bit hard for him to adapt to our system and our principles.

"We thought to give a bit more stability to the centre to switch the shape to a 5-3-2 in the second half with Jorginho.

"It was a tough one, but I hope he accepts it is my responsibility. In training it looked like he had no problem to adapt, but it was training.

"The game was very intense today, he had some easy ball losses so that’s why I thought before he loses more confidence I would take him off."