The German World Cup winner has praised the duo after their emergence in the Arsenal first-team last season.
The young duo were unlikely to have been expecting first-team opportunities last summer, given the players ahead of them in the squad, but a series of injuries saw their chances improve dramatically.
Francis Coquelin was recalled from a loan spell with Charlton Athletic after Mikel Arteta was ruled out, while Bellerin was drafted in at right-back following an injury to summer signing Mathieu Debuchy.
Both have been ever presents in the side since, and impressed, and now Mertesacker has praised the pair for stepping up to the mark and showing their potential.
“When you get some young players in and they get time to play, that is unusual for normal seasons but they hit the ground running from the start and you saw the potential,” he said.
“Not only potential, they executed it and that is something you want to see.”
The Gunners endured a difficult start to the season, with many of their players suffering something of a World Cup hangover.
However, a fine second half to the season saw them firmly challenging towards the top and become not only the Premier League’s in-form side, but one of Europe’s top performing teams in 2015.
Their season culminated in a second successive FA Cup success, and Mertesacker says that everyone being on the top of their game helps matters.
“We need everyone with us and really in form,” he added.
“That means everyone contributes, no matter where they are in the squad. That is really important for the energy of the team.”