The Gunners dominated the Hornets throughout and Iwobi was among the North London club’s best players, scoring once and creating as many as three chances for his team-mates.
It was a mature performance from the 19-year-old, and one which would have had England boss Roy Hodgson off his seat had Iwobi not already pledged his future to the Nigerian national team.
The attacking midfielder is the nephew of former Bolton Wanderers favourite Jay-Jay Okocha, and Sinclair feels that England could rue missing out on his services if he keeps up his current development.
Iwobi broke in to the Arsenal first team earlier in the campaign and made his first start for the club in the heavy 3-0 League Cup defeat at Championship side Sheffield Wednesday.
He has since become gradually more involved, and recently made his Champions League debut as he started Arsenal’s second-leg tie against Barcelona at the Nou Camp.
Having already made three caps for Nigeria, Iwobi’s international future is already set and only time will tell whether England could have done with a player of his capabilities.