In the old days, teens would begin their way into the working world by serving as an apprentice to a master of the trade he desired to pursue.

In schools across America, kids have older students or teachers act as mentors and advisers, helping them become accustomed to new things or to assist in shaping their futures.

It doesn’t exactly work that way in the dog-eat-dog world of professional football. However, having a young, promising player working behind a polished star has proven to be beneficial before.

New England Patriots quarterback Tom Brady has seen his fair share of success in the NFL. The former University of Michigan star has won three Super Bowls and two NFL MVP awards while throwing for 334 touchdowns and a passer rating of 96.6 over the course of his 14-year career.

A knee injury in the 2008 season opener sidelined Brady for the entire year, leaving the Patriots in a bind. In desperation, they turned to Matt Cassel, who was a backup behind Brady for the three previous years.

Cassel proved to be a hidden gem on the New England roster. He was an unknown to most of the football world, having spent four years as a back-up to University of Southern California stars Carson Palmer and Matt Leinart in college. Cassel saw action in just 32 games over four years at USC, never once having started a game.

But when given the opportunity in New England, he seized it and showed what he had learned. Cassel threw for 3,693 yards and 21 touchdowns in 2008, leading the Patriots to an 11-5 record, just missing the playoffs. He was traded to Kansas City in the offseason and started 15 games in each of the next two seasons for the Chiefs. Cassel passed for a combined 5,740 yards in those two seasons, and signed a $62.7 million contract in 2010.

Cassel’s high level of success was short-lived, as injuries plagued his career. After being released by Kansas City, he signed with Minnesota in March 2013, and has started one game this season for the Vikings.

Quarterback controversy has been a recurring theme for the Cleveland Browns ever since the franchise was resurrected in 1999. In the past 14 seasons, the team has seen 19 different starting quarterbacks. During the 2013 offseason, new management took a chance and signed Cleveland native Brian Hoyer — a former backup of Brady in New England — to a two-year deal.

After a stellar career at Michigan State University, Hoyer went undrafted and was signed by New England after the draft. He played in 13 games over three years with the Patriots, but was released in 2012. He had short stints with both Pittsburgh and Arizona, but was virtually unproven until coming to Cleveland.

Starter Brandon Weeden went down with a thumb injury in Week 2, and Hoyer was called upon to make the start at Minnesota the following week. He responded by throwing for three touchdowns and 321 yards, leading the Browns to a 31-27 victory — their first of the year.

The following week against Cincinnati, Hoyer posted a 103.9 QB rating, averaging 7.1 yards per pass in a 17-6 win over Cincinnati. Cleveland may have found its answer in a player born and raised just outside the city.

Both Hoyer and Cassel faced seemingly frustrating situations in New England backing up Brady. Surrounding them was the constant notion that they most likely would not see the field, and if they did, the pressure was on.

Cassel only saw action in New England due to a Brady injury. Hoyer rarely saw any playing time whatsoever. But playing behind one of the best in league history can never hurt one’s growth as a player. These two were not highly regarded upon entering the NFL, just as Brady, a sixth round pick in 2000, was not.

But when handed their one chance to shine, Cassel and Hoyer did just as Brady did: grasped the opportunity and never looked back.