But the front row ace has now agreed terms to return to his homeland from next season to bolster the pack power at Blues.
And Mitchell revealed his desire to make a big impression and repay the faith put in him by Director of Rugby Phil Davies.
He said: "I'm really pleased that the opportunity has come up at Blues and looking forward to coming back for a fresh challenge with the family.
"I have been at Exeter for three years and it's been an experience that I feel has really benefitted me. The club and coaches have been great, but now feels like the right time to come back home.
"Phil (Davies) has spoken to me about the plans at the Blues, the make-up of the squad he is looking to build and I have watched them play this season.
"They are looking to play an exciting brand of rugby and I'm keen to get my head down, work hard and be part of what I am sure will be an exciting future."