Southgate brought on Craddock for the whole of the second half and also handed Graeme Owens his senior debut with quarter of an hour remaining.
"We might have brought Graeme on earlier but he is just back from injury and we were unable to start him. Everybody knows we are happy to give youth its chance when the opportunity arises but it's always going to be tough when you have so many young players on the pitch at the same time."
Boro defender Andrew Taylor also said: "Tom showed that he could handle everything when he came on and I thought he did really well.
"I see him every day in training so I know what he is like and what he is capable of doing. His movement has always been really good. That's probably the strongest part of his game, but he's quick as well and it's a good combination for a striker to have.
"He didn't really have a chance to show exactly what he can do but I'm sure he will in the future.
"It's been a good experience for him. All young players have to start somewhere and hopefully he will be a good attacking prospect for the future."