Alvaro Negredo struck a hat-trick in Valencia's 4-0 Copa del Rey rout of Granada, which was also Gary Neville's second win in seven matches as the team's manager
Alvaro Negredo fell out of favour at the Etihad Stadium and spent last season out on loan at the Mestalla. During the 2013-14 season for Manchester City he scored 23 goals in 29 matches.
Alvaro Negredo's injury comes as Manchester City prepare to fly to the United States to continue their preparations for the start of the new Premier League season next month.
A 6-3 victory meant that City have now won all eight of their home games this season, scoring 35 goals.
Samir Nasri exploited Yaya Toure's through ball to double his team's lead in the 58th and the French international sealed the win with a brilliant finish in the 77th.
Manchester City's victory means they remain three points behind group leaders Bayern Munich and could finish top if they beat the holders at least 3-0 in the Allianz Arena on December 10.
Manchester City defender Pablo Zabaleta has warned Viktoria Plzen there will be no let-up from his free-scoring team in Wednesday's Champions League clash at Eastlands.
Manchester City manager Manuel Pellegrini admitted he cannot explain the disparity between his side's home and away form after their 6-0 demolition of Premier League rivals Tottenham Hotspur.
As expected, Manuel Pellegrini dropped goalkeeper Joe Hart to the bench as Man City hammered a hapless Norwich City.
Despite a disappointing start to the season, United have now gone six games without defeat in all competitions following a 3-1 win over Fulham at Craven Cottage.