As for what that means for the Reds' roster, C. Trent Rosecrans has these details:
Scooter Gennett out 8-12 weeks with a right groin strain. José Iglesias will play SS, José Peraza 2B. Kyle Farmer will be on the roster— C. Trent Rosecrans (@ctrent) March 23, 2019
Gennett, who turns 30 on May 1, over the last two seasons has been one of the most productive second basemen in baseball. Last season occasioned his first All-Star appearance:
As for speculation that Gennett's injury would lead to a surprise call-up for top prospect Nick Senzel, that's not the case, at least right now. As is so often the case with top prospects ready for the highest level, the team will likely manipulate his service time until they've delayed his eventual free agency by a full year. In other words, don't expect to see Senzel in the majors until at least mid-April.
Looking forward, if the Reds fail to improve in the first half of the season, then Gennett, who's in his walk year, would probably draw trade interest. If he's out toward the far end of that timeline, though, then he might not return to action until right around the July 31 trade deadline (recall that there's no longer an August waiver period for trades). In that sense, this is a potential loss on multiple levels for the Reds.
As for the fantasy implications of the Gennett injury,.