Is it a dynasty league? In most keeper leagues you wouldn't be keeping a Middle Reliever.
So my answer is this: If it's just for one year, take Gordon with the knowledge that he's old and has a long injury history but is very talented. I wouldn't count on the same numbers you got this year from Flash. Personally, he's too high risk for me to justify taking him where he'll go, but you are a different breed, Rico.
If it's for more than one year, go after someone else.