Sunderland squad boost for Newcastle United 'target' Chris Rigg
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Rigg, not 16 until next June, has trained with the first team after making the bench for the 1-1 draw with Blackpool.
He could well be joined on the bench by 16-year-old Tom Watson, with nine substitutes allowed in the FA Cup.
"Chris is coming with us," Mowbray said.
"I watched him train today with the first team in our game preparation stuff and he was very impressive for a boy, and a slight boy at that. He's got a wonderful left foot and he is an incredibly competitive animal. It was really interesting for me to watch him - I have to say that the potential looks enormous.
"He looks like someone who is going to play with that silkiness with the passing on his left foot and he looks to have that tiger in him as well, he wants to tackle everyone. It's not a bad mix for a midfielder. He's a boy of 15, I don't want to build him up too much other than to say that from what I've seen he warrants being around our squad."
Mowbray will give opportunities to youngsters throughout the game but also said that his priority first and foremost was ensuring a performance for another sold-out away end.
"The first priority is to go there, perform well and win the match," he said.
"If the opportunity comes to blood a young player in an environment we feel comfortable in, we will do that.
"The first thing is for the people who pay their money, travel for five or six hours and get home late on Saturday night - we have to try and win the match for them. There is a balance, I want to develop younger players but I want to win every game for all these people travelling for hours to watch us, spending their money and eating bad food in service stations. We have a responsibility to try and compete and try and win."