The Academy graduate, who won the 2006/07 Jimmy Murphy Young Player of the Year award, joined Watford just a few weeks before Ighalo arrived from Udinese in July 2014.
During a three-year spell, the pair were part of a successful period for the Hertfordshire club, which included earning promotion to the Premier League and then flourishing in their first season back in the big time.
Now Ighalo is poised to return to top-flight action, after agreeing a loan deal to join the Reds from Chinese club Shanghai Shenhua, and Cathcart is excited about the contribution his erstwhile colleague could make up north.