Comolli was in Dublin yesterday as part of the Web Summit, and revealed how he got “so much criticism” for signing the England man.
Henderson moved to Liverpool in 2011 for £20 million, but failed to shine in his first season.
The former Sunderland man is now club vice-captain — but performed poorly in his first two seasons at the club.
“When we signed Jordan Henderson, he got so much criticism, I got so much criticism,” Comolli said. “I was never told why I was sacked but I was led to believe it was because we signed Jordan Henderson, and the owners were convinced he was not good enough.”
Comolli says statistics played a big part in the transfer policy at Anfield in his time, and were integral to the club signing Luis Suarez.
Comolli said Liverpool had relied on the “eyes, ears and numbers” formula to evaluate Suarez while he played in Holland.
“We’d watched him since Groningen, so we were aware of what he did, how he played and so on. That was the ‘eyes’ part,” said Comolli.
“Numbers? We didn’t have a lot of data on the Dutch League at the time, but we knew he’d scored 41 in 61: numbers.
“We tried to measure what goals in other leagues would be ‘worth’ in the Premier League. It’s not perfect but we felt a goal in Holland was worth one-10th of a Premier League goal.
“So we felt he wouldn’t get 41 in 61, but we were wrong — he got 31 in 33 games.
“We looked at other factors — how and when he scored, did he score when they were chasing the game or when they were three-nil up, did he get equalisers, could you rely on him to score away from home, did he only score against weak teams or against top teams.
“Did he create chances, did he deliver assists, how did he play in the last third?
“Another question was personality. We needed personality up front, — would he be a technical and emotional leader for the team at the front and give it that spark?
“When we looked at it, he gave us everything.”
Comolli says the last part of the equation then came into play.
“Our chief scout heard that we could do the deal, that they (Ajax) wanted to sell him: ears. We couldn’t believe it and decided to move.
“We heard people saying he couldn’t play in the Premier League — Spurs had him, but they decided he couldn’t play in England, so they moved away.
“They heard we were interested and tried to move in, but it was too late.”
Comolli also said that statistics contradicted an article of faith in field sports, that young players can play more games because they recover quicker.
“Measuring the load the young player can take, you want to ensure that when he becomes a mature player at 23 that he’ll continue like that for 10 years.
“At Liverpool we had devices to measure player load, we had five and tried them on young players. At the time John Flanagan was in the first team, he was 18 but playing quite a lot.
“What we found out went totally against everything I’ve heard since I was brought up in football, that young players can play more because they recover quicker.
“Rubbish. We found that John Flanagan’s heart rate was coming back to normal 72 hours after a 90-minute game, whereas a senior player was coming back to normal 24-36 hours later. That meant the risk of breaking down for him, if we played him within 72 hours of that game, was massive.”