INDIANAPOLIS (Reuters) - New England Patriots head coach Bill Belichick and New York Giants counterpart Tom Coughlin won a Super Bowl together 21 years ago but on Sunday they will be doing all they can to outsmart each other in the championship game.

The relationship between the two experienced coaches with a combined four Super Bowl wins as National Football League (NFL) head coaches dates back to the days when they worked under as assistants on the New York Giants.

Between the 1988 and 1990 NFL seasons, Belichick was a defensive coordinator for the Giants and in charge of the secondary while Coughlin was a receivers coach.

It was a combination that Belichick described in warm and affectionate detail on Monday after his team's first Super Bowl practice at the Indianapolis Colts' training facility.

"We worked together every day in one-on-ones and seven-on-sevens ... I would run the coverages in the way he wanted them run, based on who we were playing and he would run the patterns the way I asked him," said Belichick.

"I would say that as an assistant coach it was the best relationship that I have ever had with another counterpart in that way."

More than just running simulations of an upcoming offense, Coughlin offered Belichick's defensive backs insight into the thinking and the strategy that receivers would be armed with.

"We had a very good give-and-take on a daily basis, whether it was in training camp or whether it was on a weekly or daily game preparation basis .... we were able to help each other out and help each other coach their position better," he said.

"It was not only good between us but it transcended the units we were coaching and the players that we had. It was a great working relationship with Tom, it was outstanding, it really was."

The partnership reached fruition with the Giants' Super Bowl win over Buffalo to conclude the 1990 season and then they went their separate ways.

Coughlin then spent three years as the head coach at Boston College before landing his first NFL head coaching position with the Jacksonville Jaguars while Belichick stayed in the league and took charge of the Cleveland Browns.

But the lessons learnt from their time with the Giants have clearly influenced Belichick as he has sought to instill the same exchange of information in his own staffs over the years.

"I wish that every position coach could have that with their counterpart on staff. Sometimes you do, sometimes you don't. But that was really exceptional, I learnt a lot from Tom, relative to the offensive point of view, the passing game," he said.

Belichick, who has won three Super Bowls with the Patriots but lost four years ago to Coughlin's Giants, also knows he is up against a man who has honed his skills as a head coach.

"I respect a lot of things about Tom - his evaluation of talent, the way he attacks teams, his consistency, his discipline, his team's toughness and resilience."