It should be noted that during his team's most recent game, Gallagher appeared to injure his lower body and retreated to the infirmary, before eventually returning to the game, but he was clearly not at 100%.
The good news, however, is that the young Juraj Slafkovsky seems to have returned to a normal and regular training pace, which could indicate that he is back to 100% after having been several days without practicing with his teammates. (He hasn't missed any games, however.)
As for Gallagher, the 31-year-old forward has accumulated 20 points in 64 games, including 11 goals. He earns 6.5 million dollars per year until 2027.