Need help with catching injured feral!

I've been trying to trap an injured feral cat for two days now with no luck and I could really use some advice. The cat is cared for by a couple and he spends time in their yard and a shed they have set up for the cats. The cat was in the shed when I got there two days ago but once he saw me hauling traps he took off. I don't know if he's been back but I've stayed away today in hopes that he will come back with me gone.

He has an injured leg and possibly one or more injured paws. His caretakers say that his paws look really bad and one paw/leg is swollen and he is limping badly. He did however climb a fence to get away from me and my traps.

I've had three traps set baited with Fancy Feast or tuna and not caught this cat or any of his friends. I thought about baiting with sardines tomorrow. Any other suggestions?

I'm worried that every time I come to check the traps I scare him away if he's nearby. How long do you guys think I can safely leave the traps?

I really didn't think I'd have this hard of a time catching him. Any suggestions for how to get him would be greatly appreciated. This little guy is suffering and needs to get to the vet.

I would leave the traps as long as needed.  Make sure the couple do not feed him at all, though, or there will be no reason for him to go in.

If they have to feed the other cats and he can get to it, perhaps a drop trap will work.  That way, you can pick the time (and cat) to spring it.  You can modify a regular trap to act as a drop trap.

Place a bottle filled with rocks under the door.  Tie a length of twine or rope around the bottle so you can pull it out from under the door when the right cat goes in.

It sounds like he may be trap savvy, although the hub-bub of setting them up may have spooked him a bit.  Perhaps when they become part of the landscape, he will be less scared.

I just went through something similar with an injuried feral. Use tuna fish & sardines to really entice him in the cage. Put some oil from the tuna on the outside of the cage and in the entrance so it really gets stinky. When he is hungry enough he will go in.. Mine went in 2 times in one night( first time we picked it up & the door opened!!) good luck!! Your doing a great thing for him