A single IF from Danny can take Cap out if landed directly. But... a single hit from Cap can also take out Danny if landed properly, or at least knock him down and hurt him. It's going to be very hard for Danny to land that IF when Cap is hitting him with superhuman strength and being skilled and fast enough to keep up with him. It would be like fighting a Daredevil enhanced with Jessica Jones' strength. Danny won't be able to take more than a few hits from Cap whereas Cap can tank pretty much everything Danny throws at him other than the IF.
In the end I have to give Cap the win, maybe 7/10. Danny winning 3/10 by lucky shot of his IF. And that's only h2h. Give Cap the shield and I'll go 10/10 in favor of Cap.