Definitely try to catch him. Rabbits typically don't do well outside in the winter and mini rexes are particularly not suited to living outside in the cold. It is summer now, so you do have time.
If you have an x-pen or something similar, try setting that up to make a smaller space, but be able to close it. Leave it around so he can get used to it and even leave some food, water or a hiding space inside the pen. Try to hang around a bit so you can close the pen when he is inside. If he will come to you in the pen, you can sit at the far end and have someone else close the door. This will get him in a confined area which will make it easier to catch him and hopefully not cause too much stress.
Try to have a space inside where you can keep him, even temporary. Offer pellets, hay and some grass to start with as well as water.
