He has missed a seasons worth of football in the past 2 years. There's no doubt that he's injury prone. In the past 4 seasons, he's only had one that hasn't been injury ravaged. Missing 1.5 seasons worth of games in 4 seasons is a shocking fitness record, especially when a bit extra would be needed for match fitness. With all of his fitness issues, injuries and age, Schweinstiger doesn't have the stamina to play as a no 8 like Schneiderlin does.
You can't say i'm, trolling when everything i've said is logical.
Fellaini and Herrera are more qualified as holding midfielders than Schweinstiger. At least Fellaini has been proven there, he's more adept at getting around the pitch and is a much better tackler.