The 2015 season is Roethlisberger’s final year of an eight-year, $102 million contract that he signed in 2008.
"You have seen it with a couple of great players that are still playing in Peyton Manning and Tom Brady. Their games have certainly not deteriorated," Colbert said to the Pittsburgh Post-Gazette. "I really think Ben is going to be a better quarterback down the road than he has been up to this point.”
Roethlisberger, 32, tied for the league-lead with 4,952 passing yards while setting a career-high in completion percentage last season. His 32 touchdowns in 2014 tied a career-high.
Roethlisberger told a Pittsburgh radio station last month that he hopes to sign a new deal “sooner than later.”
"I think those guys still have another level they can reach," Colbert said. "I think by them reaching another level, it will make Ben's job a little bit easier. I think that part of Ben will grow as the players around him grow, if he has the right players around him. I think they are heading in that direction right now."
Roethlisberger has spent his entire career with the Steelers after he was selected in the first round of 2004 NFL Draft, and has led Pittsburgh to two Super Bowl titles.
The Steelers won the AFC North with an 11-5 record last season and lost to the Baltimore Ravens in the Wild Card round.
- Scooby Axson