"But I am happy for him that he scored a goal after that and I'm sure that he will continue to score goals and that he will score many this season", Matic added.
Lampard has no doubt that Matic's arrival will make United stronger.
Manchester City, along with United, are the two early favourites for the Premier League title given the money they have spent on strengthening their squads so far this summer. Asked about their ambitions, Mourinho said: "Yes we can win [the Premier League]".
"Being the main striker for a club like Chelsea, like Manchester United, like Real Madrid, like Barcelona, brings a lot to it", Lampard said. Lampard does not believe the situation will make the Frenchman's adaptation to the Premier League harder, but he conceded that the challenge facing the 22-year-old is a significant one.
Despite having only played 45 minutes for the club in last week's friendly against Sampdoria, the £35million signing impressed throughout the whole match in sweltering Macedonia.
Fellow summer signing Lindelof struggled at times in a United defence that was missing several players through injury or suspension against Zinedine Zidane's Champions League winners. Was it his dream to go and play for Manchester United?
"He seemed like he wanted to leave previous year at times, although he was very influential and played very well", he said of Costa. "But he is a great loss for us".
"He's very similar in a way to Michael Carrick - a controlling midfielder. They allowed [Eden] Hazard, [Cesc] Fabregas and whoever else was playing that bit of freedom and I'm hoping he'll do that for United for [Paul] Pogba, [Anthony] Martial, [Jesse] Lingard and [Henrikh] Mkhitaryan". "It would be silly to dismiss Chelsea after the way they played so dominantly previous year but looking at the teams, I think City and United will be up there and the teams to watch".