Here, Press Association Sport looks at the German side.
How the tie is poised
City lead 3-2 after an eventful first leg in the Veltins Arena three weeks ago. Former Schalke player Leroy Sane equalised with an 85th-minute free-kick and Raheem Sterling scored a last-gasp winner as City came from behind. City had led through an early Sergio Aguero strike but two penalties from Nabil Bentaleb – the first controversially awarded following a VAR review of a handball by Nicolas Otamendi – turned the match around. Otamendi was later sent off for a second bookable offence.
Schalke have failed to replicate the form that saw them finish second in the Bundesliga last season and are enduring a miserable campaign. They are currently 14th in the table and have won just two matches in 2019, one of which was in the German Cup. Their best performances have come in Champions League, in which they finished second in Group D to Porto. They do have some Champions League pedigree having reached the knockout stages on five previous occasions in the past decade, including the semi-finals in 2011.
Wales winger Rabbi Matondo, 18, joined Schalke from City in an £11million deal in January. He is a highly-rated product of City's much-vaunted Academy but never came close to first-team recognition. Defender Matija Nastasic is another ex-City player. The Serbian made 34 Premier League appearances between 2012 and 2014. Bentaleb and Benjamin Stambouli have also played in the Premier League for Tottenham.
Domenico Tedesco is under severe pressure, with some reports in Germany suggesting that it is only because Schalke remain in the Champions League that he is still in a job. The 33-year-old Italian-born German took over at Schalke two years ago having previously managed second division side Erzgebirge Aue.
City overcame Schalke in the semi-finals of their victorious European Cup Winners' Cup campaign of 1969-70. The Germans won the first leg at home but City roared back with a 5-1 success at Maine Road. More recently they met in a one-off UEFA Cup group match in 2008. City won 2-0 in Gelsenkirchen with current captain Vincent Kompany in the side.