United secured the signature of James from Swansea this week, as the 21-year-old dotted the i's and crossed the t's on his contract.
Other clubs were interested in James, but it appears the influence of his national team boss and United legend Giggs swayed him in favour of the Red Devils.
"Yeah, Ryan was obviously a big credit to why I'm here now," he said in an interview with MUTV.
"Obviously he gave that opportunity to me in the Slovakia game, and to score in the first five minutes was amazing for me.
"I think the trust he's given me, and from then on he's watched a few games of me at Swansea... he's a big credit to why I'm here now.
"Obviously he mentioned me here and I'd give a lot back to him for that."