Pro Bowl tight end Aaron Hernandez has signed a lucrative five-year contract extension with the New England Patriots, the NFL (National Football League) Network reported on Monday.

Financial terms of the contract were not disclosed but media reports estimate the deal, which would keep the 22-year-old in New England through the 2018 season, to be worth $37.5 million.

Asked by reporters about the contract extension, Patriots head coach Bill Belichick replied: "We wouldn't have done it if we weren't happy with it. I'm glad it worked out.

"Aaron has improved a lot. He's worked hard, he's improved a lot in all phases of the game: passing game, running game, protection and his overall versatility. He's done a good job for us."

A fourth-round pick by the Patriots in the 2010 NFL Draft, Hernandez was selected for the Pro Bowl after his second season in the league, and helped New England win the AFC Championship Game before they lost to the New York Giants in the Super Bowl.

In his two seasons with the Patriots, the University of Florida standout has started 19 of 28 games and has 124 receptions for 1,473 yards and 13 touchdowns, with eight rushing attempts for 92 yards.

"He's a hard guy to cover," said Belichick. "We've had a lot of trouble covering him defensively."

The Hernandez deal follows a six-year contract extension signed by his fellow All-Pro tight end Rob Gronkowski with the Patriots early in June.