Ole Gunnar Solskjaer claimed Bruno Fernandes had energised "the whole club" after playing a starring role in Manchester United's derby victory over Manchester City.
United boss Solskjaer also hailed the character of the January signing after he had the last laugh in a heated exchange with City manager Pep Guardiola late in United's 2-0 success at Old Trafford.
Portugal midfielder Fernandes, who set up the opening goal for Anthony Martial, put his fingers to his lips after arguing with Guardiola moments before Scott McTominay sealed victory in injury time.
Asked how Fernandes had lifted the team, Solskjaer said: "(It's) the whole club, because he has everything. He works hard and he is humble enough.
"He has the desire and commitment but he has also got the X-factor, he is a risk-taker. He has the courage, he is brave enough to make mistakes and if you make enough mistakes it'll be corrected into fantastic assists or goals."
Asked specifically about the incident involving Guardiola, Solskjaer said: "You need character at this club but this team they have got that. They have learned through some hard times this season. We have started something we believe in and Bruno has helped that."
Fernandes' arrival does seem to have kick-started United's campaign with the team unbeaten in eight games in all competitions since his debut.
Their latest victory lifted them back to fifth in the Premier League, three points behind fourth-placed Chelsea.
The win also completed United's first league double over City for 10 years.
Solskjaer said: "We feel we are improving all the time. We know we lack one or two, three players, and some experience, to be considered a title contender.
"But we are not going to start talking about that now. We are just going to start talking about going up the table, getting more points, to that top four.
"Chelsea and Leicester are still too far ahead for my liking still.
"For me it shows we are on the right track and we're improving and we are Man Utd. We are looking towards catching the teams in front of us.
"But this is one game. Now it is on to Thursday and Sunday, two big games for us."