Roy Keane's playing career saw him represent Nottingham Forest, Manchester United and Celtic.
Howard has represented the likes of Manchester United and the USA national team during his time in professional football, but nobody has impressed him as much as Keane.
"He was probably the greatest player I've played with; a brilliant captain, able to marshal a game with just his voice, and an intimidating figure - but I respected him because he played the right way," Howard said in the Liverpool Echo.
Keane had a glistening playing career at the top level, with the Irish midfielder going on to become a club legend at Old Trafford.
His powerful displays in the centre of midfield made him one of the Red Devil's heroes throughout one of the most successful periods of their history.
Keane also played for Nottingham Forest and Celtic during his playing days, although his spells as these two clubs were much more brief that his time at United.
Keane played for Forest between 1990 and 1993, before retiring when he got to Celtic in the 2005/06 campaign.
Since retiring from being a professional, he has gone onto a career in management. Keane has taken charge at Sunderland and Ipswich Town, while he currently works as Martin O'Neill's number two for the Republic of Ireland.