Harnik dislocated his shoulder in Stuttgart's 0-0 draw at Hannover last week, which took the relegation-threatened Swabian club five points clear of the Bundesliga's drop zone with two games left.
Stuttgart will host high-flying Wolfsburg in the penultimate round knowing a draw should be enough to secure top-flight football for next season, and Harnik could play after the 26-year-old was involved in training on Tuesday.
Huub Stevens' Stuttgart have not lost in four games as they attempt to avoid relegation and Georg Niedermeier believes the Dutch coach's focus on defence has been crucial, as his side have conceded just two goals in that period.
"Stevens values defensive work greatly and that has worked very well for us of late," the 28-year-old defender said.
Harnik trained away from the main group in Stuttgart's first session following Saturday's draw but is expected to take part in full training later in the week in the hope he can prove his fitness for the match against Wolfsburg.
The winger is Stuttgart's equal leading goal-scorer in the Bundesliga this season alongside Vedad Ibisevic with 10.
Dieter Hecking's Wolfsburg have lost just one of their past eight Bundesliga games and have 54 points in fifth, four more than seventh-placed Mainz, who sit just outside the European qualifying berths.
Mainz travel to sixth-placed Borussia Monchengladbach, for what shapes as something of a winner-takes-all encounter, in terms of Germany's second UEFA Europa League berth.
Schalke have lost their past two games but will wrap up third spot and an automatic berth in next season's Champions League if they get a better result against Freiburg than fourth-placed Bayer Leverkusen manage at Eintracht Frankfurt.
