I guess the Reds don't really need outfielders as they have like six on their roster but point being is that Gurriel's contract makes him a valuable chip that should be cashed in also on someone with control.
If you can move a corner OF to shore up other areas of need then pull the trigger. Every year there are a bunch of guys available on short contracts to plug into LF. This year there are guys like Schwarber, Rosario, Pederson, Grossman or even Brantley who could all be had relatively cheap or short term.