McClaren was at Tynecastle on Wednesday night to watch the quartet in action in the 2-0 win over Rangers. He had been advised by scouts to watch them in person.
The former England manager stated he was also taking the chance to look at Rangers but explained why several Hearts players impressed him.
“Our scouts have been out and about,” said McClaren, whose club are currently ninth in the English Championship.
“They have talked about Rangers doing well, and they have got some good players, and there are four or five in the Hearts’ team, also.
“Yes, people are talking about Paterson but the Souttar boy at centre-back, Johnsen up front and Walker boy playing out wide – there are about four players the scouts said, ‘yes, have a look at them’.
“It was a great opportunity to go up and do that. We are always on the lookout and keeping track of players, and that’s why I was there.”