Otamendi, 31, signed a contract extension in January but has started fewer than half of City's Premier League and Champions League games this season, with Pep Guardiola having four top-class centre-backs to choose from.
City could even bring in a new defender, with Matthijs de Ligt of Ajax a potential target amid Kompany's injury problems.
Otamendi is happy in Manchester but could leave if the right opportunity came up.
Meanwhile, Danilo has made 12 appearances in the Premier League and Champions League this season.
The 27-year-old was affected by an ankle injury early in the campaign but impressed over Christmas when he started six successive games, including the potentially key home victory over Liverpool.
But he has failed to dislodge Kyle Walker as Guardiola's first-choice right-back and a number of clubs, including Inter Milan, have shown interest.
Both Danilo and Otamendi were back in training on Monday, with City needing two victories from their last two matches to secure a second successive Premier League title.
Fernandinho twisted a knee in the victory over Manchester United earlier this month, while De Bruyne injured a hamstring in the win over Spurs four days earlier.
Both face a race to be fit for the FA Cup final against Watford at Wembley on May 18.