Northampton make the trip to Tyneside on Tuesday looking to cause an upset against a side that earned a goalless draw at Manchester United on Saturday.
Having seen cup competitions take a back seat over the past few years, it seems Newcastle fans will be seeing a strong starting line-up tonight and McClaren told his club's official club website that he has had the Cobblers watched over the past few games.
"They are physical, strong and put in lots of crosses," said the former England manager.
Northampton's new loan signing, Adam Yates from Port Vale, may make an immediate debut with Josh Lelan suspended for one game following his dismissal against Plymouth Argyle at the weekend.
Manager Chris Wilder is hoping the 32-year-old right-back will add some experience to his defensive options while Jason Taylor is available after serving a one-match ban against the Pilgrims.