Diego Costa scored in the 23rd minute to ensure an important win over Arsenal on a Super Sunday. In another game, Swansea fought hard for a 2-1 win over Everton.
Arsenal breathed some life back into their Champions League with a 2-0 win over Pep Guardiola's Bayern at the Emirates Stadium a fortnight ago in Group F.
French international footballer Koscielny has not fully recovered from a back injury which kept him out of Monday's Liverpool game while Mertesacker, member of the 2014 FIFA World Cup-winning German side, is also still ill.
Petr Cech moved across the English capital last month from Chelsea where he won four Premier League titles and the Champions League in 11 successful seasons.
Arsenal demolished Aston Villa 4-0 to lift the FA Cup for the 12th time. Arsene Wenger became the first manager in the post-War period to win the competition six times.
World champions Germany have managed just four points from their three Euro 2016 qualfiers. Retirement of big stars and injuries to some of the current heroes in the team has compounded the problem.
Per Mertesacker has become the third member of Germany's World Cup-winning team to announce his international retirement.
A 6-3 victory meant that City have now won all eight of their home games this season, scoring 35 goals.
While Arsenal hope to cement their position at the top, fourth-placed Manchester City can't afford to lose their 100 percent home record if they want to stay in touch with the leaders.
After a brilliant start to life in England following his move from Real Madrid on transfer deadline day, Mesut Ozil has produced a few under-whelming displays of late and Mertesacker believes Ozil will quickly silence any critics.
The sides' first meeting since Germany's bruising 4-1 win in the last 16 at the 2010 World Cup in South Africa was decided by a 39th-minute header from Arsenal defender Per Mertesacker.
The Gunners travel across London to face struggling Crystal Palace on Saturday after Robert Lewandowski's late winner secured Borussia Dortmund's 2-1 victory at the Emirates Stadium.
Goals from Ramsey and Per Mertesacker sealed Arsenal's victory.
His purchase was widely regarded as something of a panic buy by Wenger after Gael Clichy's move to Manchester City and the Brazilian was unable to disprove that theory with his performances.
The 30-year-old fell out of favour with Gunners manager Arsene Wenger last year after managing just 23 first-team appearances in 18 months.
Tottenham striker Dempsey netted his 34th and 35th international goals in his 96th appearance for the USA, moving past Eric Wynalda into second on the all-time US scoring list, 14 shy of Landon Donovan's record.
The Brazil international has played 36 games for Arsenal since signing in August 2011, but has fallen behind Kieran Gibbs and Nacho Monreal in the pecking order.
With Andre Santos already on Arsenal's books, Wenger now has three specialist left-backs at his disposal, but Wenger says it is important to have cover in the position.