It is surely enough, even 1 goal is enough. The most important thing that Inter Milan could get 3 points in the match. They need full points to keep their position in the top standings of Serie A. They must be very careful because Juventus is in 2nd place and only have 2 points difference.
Inter Milan must play more safely and carefully because they are going through a tough season because they have to face a busy match schedule. So making small mistakes can provide an advantage for Juventus who are not too busy taking part in many competitions at the moment. A one goal win is more than enough and the coach must ensure that his players are fit to play.
Inter Milan must be aware about the potential drop in their performance. They need to keep their motivation in competing the title. The bigger challenges will happen in the second half, sometimes many teams drop their performance when it is toward the second half. You're right that one of the solution is about rotating the players on the starting lineup. Inzaghi needs to try this way, it also minimizes the chance of injuries among the players, too.
This will become a big problem when several important players experience fatigue which results in fatal injuries. Inzaghi also has to rotate his players in matches that are not too tough, but he has to see the right timing so that they don't lose. The second half of the season will be even busier because if they manage to qualify for the next phase in the Champions League then the matches there will be much tougher because they will face much stronger teams. The real worry will occur in the second half of the season because coaches will not be able to rotate injured players because they may not have suitable replacement players.
Being runner-up in the previous season definitely targets winning the Champions League this season and this is not an easy job because if Inzaghi fails to take advantage of the opportunities that exist it will have fatal consequences. Because Inter Milan could lose the opportunity to compete for the Scudetto or win the Champions League.