I agree that Lautaro Martinez is a key player and his absence would be a huge loss for the team, but they would still not be left without chances. What is so strong about Inter Milan this season is the stability within their team straight through from the defense to the offense. It would weaken their offense and hence the entire game, but it would still not be easy to score against Inter Milan and that is something they are even doing better this year than last year. But in the Champions League obviously you always want all the best players to be healthy and available.
Inter Milan this season is quite strong and the strength of this team extends across all lines, although it cannot be denied that Lautaro Martinez is their mainstay on the front line, but that does not mean that the performance of the Inter Milan team will really depend on Lautaro Martinez.
With what Inter Milan showed in their Serie A matches and also their achievements in the UCL last season, it is only fitting that Inter Milan is favored and taken into account for the title race this season.