Manchester United are playing with the killer instinct they lacked last season but manager Jose Mourinho still wants more goals. A promising first campaign in the Old Trafford dugout could have been improved markedly had Zlatan Ibrahimovic's goals been better backed up by team-mates.United won the Community Shield, EFL Cup and, most importantly, Europa League, although Mourinho regularly bemoaned his side's inability to finish teams off.It proved particularly costly in the Premier League as they stumbled home sixth having netted just 54 goals - a goal ratio of 1.42 that has improved to an average of three per game in the opening weeks of this season.Leading man Romelu Lukaku's four league goals have been complemented by efforts from five other players, but Mourinho is not satisfied by the table-toppers' improvements."I am very pleased with the contribution but I want more goals," he said. "The way the team plays, they have to (score more goals)."When a team doesn't create a lot, when a team doesn't have the ball, when a team is just reactive, it is more difficult for these players (in attacking positions)."But when the team is in control and makes decisions on the direction of a game, when the team is so offensive, when the team puts so many people in attacking areas, I think they have to score goals."It's not just about the striker."A striker is very important but last season we had a very good striker for two thirds of the season and that was not enough to win the title, so it's not just the striker."I think that Romelu has a better team than Zlatan had. Romelu's team plays different football and the confidence levels are different and it is a team in the second year of its evolution in some aspects."But I think he also deserves credit for that because of the way he plays, the way he is committed, what he does with and without the ball, not just the last touch and the goal but his overall contribution. We couldn't be happier (with him)."Lukaku faces former club Everton this weekend having netted six goals in as many matches in all competitions for United since his Â£75million move.Sunday's encounter also see United's all-time top scorer Wayne Rooney make his first return to Old Trafford since heading back to his boyhood club.The 31-year-old netted 253 goals in 559 appearances for the club while collecting trophies aplenty - achievements Mourinho believes someone like Lukaku will find hard to match, no matter his quality."Wayne arrived much earlier than that," the United boss said of 24-year-old Lukaku. "I think Wayne spent probably 10 years of his career in a different Premier League than you have now."A Premier League where it was easier to score goals not just because of the difference between the top teams and others but also because of the profile and the tactical interpretation of the competition."I think this Premier League is much more defensive-minded, and much more difficult."Another man with links to both sides is Marouane Fellaini.Last December the divisive midfielder clumsily gifted former club Everton the penalty that allowed them to snatch a 1-1 draw at Goodison Park - something that led some sections of the Old Trafford faithful to jeer him in United's next home match.However, Mourinho has kept faith with Fellaini and continues to back him, with the midfielder an option to replace the injured Paul Pogba on Sunday."What I did with Marouane is what I do normally with every player," he said."Like (Phil) Jones, he made a bad mistake for Stoke's second goal. Did I kill him? No. Will he be on the bench on Sunday? No."So life goes on, and that's the way I did it last season with Fellaini."When players make one individual big mistake and everybody knows that they did it, the players are the first to know they did, and they don't need any more criticism from the manager that they get from the fans or from the media."It's just being pragmatic and showing common sense."