The young defender is said to have been watched by 22 scouts when the Black Cats faced Crewe Alexandra earlier this year.
Doyle also started for Sunderland against Arsenal in the Wearsiders’ Carabao Cup quarter-final loss.
Speaking about Doyle to Football Insider, Phillips said: “Let’s not get too carried away.
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“He is still a very young lad and is developing. Physically, he will get more muscular as time goes on. Even though he is big lad, he is still young.
“He has all of the attributes to be a top player though. He’s aggressive and has a great left foot. It is important we don’t get too carried away though.
“I’m not surprised scouts are looking at him though. His form doesn’t worry me because he is a young kid. Every player goes through a dip in form.
“I was impressed with him the other night though. He’ll learn from it, I’m sure. I think he’ll be one of their key players between now and the end of the season.”
League One rivals set to bag striker
Lincoln are set to enjoy a successful conclusion to their pursuit of Swansea striker Morgan Whittaker.
The Imps are said to be close to landing the 20-year-old on loan in January.
Michael Appleton was keen to bring in Whittaker before the close of the summer window, but couldn’t get a deal over the line.
The 20-year-old, who joined from Derby County last summer for £700,000, has had to be content with just three Carabao Cup starts this term.