Roberto Mancini has challenged Manchester City striker Jo to keep up the good work following his goal in the Europa League win over Salzburg.[LNB] On his first competitive start for City since December 2008, the Brazilian scored for the first time for the club since September that same year to seal a comfortable win for the Blues in their Group A opener.[LNB]It represents a remarkable transformation for a player who has spent 18 months of the two years since a £17million move from CSKA Moscow out on loan, first at Everton, then, after falling out with David Moyes, Galatasaray.[LNB]But, having responded in the best manner possible to an unexpected opportunity created by the injuries to Emmanuel Adebayor and Mario Balotelli, Mancini now wants more from Jo.[LNB]"To me, my players are the best in the world," said the City chief. "But I know for all strikers it is important to score goals.[LNB]"Jo has scored one important goal for us. Now I hope he continues to play in the same way."[LNB]Jo also created City's seventh-minute opener for David Silva, who put a difficult period behind him, stroking the Blues in front expertly from his team-mate's lay-off to cap an eye-catching performance that will silence the criticism that has started to grow around the Spain international.[LNB]"David is a fantastic player," proclaimed Mancini.[LNB]"But he is in a different situation now playing different football.[LNB]"After one month he is ready to go 100 per cent for the team.[LNB]"He will also be an important player for the future."[LNB]After returning late due to his World Cup commitments and then jetting off to Mexico and Argentina on international duty, it has not been an easy couple of months for the £24million capture from Valencia.[LNB]However, he showed glimpses last night of what a valuable asset he is likely to be this season.[LNB]And, while Silva's prowess on the European stage is well known, Mancini is convinced he has the physical strength to cope with the battering he will doubtless encounter in the Premier League.[LNB]"He knows how to play football," he said.[LNB]"Arsenal have two or three players like David and they play very well.[LNB]"He is a strong player who can play in every position.[LNB]"He has played for Valencia in the Champions League for many years.[LNB]"But the Premier League is different and every player needs one or two months to understand English football."