Putting the injury aside it's hard to even justify keeping him as his returns this season aren't justifying the price imo. Gundogan is comfortably outscoring him since starting regularly for half his price.
Points over the last 7 gameweeks...
* KDB - 39
* Gundogan - 54
That money saved can turn a Watkins into Vardy or Kane for example.
I agree, but this surely gotta be a spike in Gündogan's numbers, as we all know Gundogan has not performed at these numbers in other seasons.
So if he has overperformed now (he's playing like Xavi at the moment btw), he might be in for a dip in goals/returns. However at his current price, if we correct for the projected dip in goals, he might still be great value compared to his price.
I might go KdB to Gundogan if KdB's out for more than 1 gw, but KdB should return to his old form sooner or later with so many easy games. Against the opposition KdB has he's realiable and great captain material - I don't think I can rely on Gündogan.
Edit with statistical analysis over last 10 games:
Now that I take a look at their stats pr 90 minutes for the last 10 games, their numbers and areas they operate in are not that far off:
Gündogan: xG: 0.4 - xA: 0.1
De Bruyne: xG: 0.5 - xA: 0.3
Goal conversion: Gündogan 20.8, Kdb 5.7 which says something about how bad KdB has been on big chances this season and how Gündogan on the opposite has taken his chances.
So Gündogan seems the obvious transfer if De Bruyne is out. Maybe even if he's not to free up funds, as you suggest.