Tom Brady won six Super Bowls with the Patriots, and New England has not won a playoff game since he left for Tampa Bay after the 2019 season. Dave Martin/Associated Press

When a generational talent arrives, he can turn a franchise around. How a franchise handles losing a generational talent can define it for years.

Tom Brady came to Foxborough, Massachusetts, as a sixth-round pick and left as the greatest quarterback in NFL history. He led the Patriots to six championships and made New England the envy of the football world.

Brady left after the 2019 season and won a seventh Super Bowl with Tampa Bay. The Patriots haven’t won a playoff game since. They’ve been the league’s worst team over the past two years with back-to-back four-win seasons.

We’ve lived through multiple quarterbacks, head coaches and football executives. Jerod Mayo is the most recent casualty of the Patriots’ futility, fired shortly after Sunday’s finale. Whoever replaces Mayo will have a star-in-the-making quarterback to build around. Drake Maye is the first Patriots quarterback to inspire confidence since Brady.

Would things have played out differently had Brady stayed? Could he have led the Patriots to more success in 2020 or 2021? Would that have given the Krafts the confidence to spend more on the roster around him?

We’ll never know.

In the months after Brady’s departure, the Red Sox believed they could not convince Mookie Betts to stay in Boston before hitting free agency. They feared losing him and getting nothing in return.

Mookie Betts won the American League MVP and led the Red Sox to the World Series title in 2018. Boston traded him to the Dodgers after the 2019 season and has made the playoffs just once since. Charles Krupa/Associated Press

Chaim Bloom was brought in to trade Betts. He threw in David Price to get under the competitive balance tax and got three Dodgers in return. It was a shocking deal, the Sox sending their best player in a trade that brought in Alex Verdugo, Connor Wong and Jeter Downs.

The Red Sox thought they were being proactive by trading Betts. They thought they could get a return on their biggest asset. They thought it would start the rebuilding process as they transitioned from the core group that won the 2018 championship.

Instead, they’re still rebuilding. The Sox are in the midst of the longest run without a championship in the Fenway Sports Group era. Wong is Boston’s starting catcher, but Downs ended last year playing in Japan and Verdugo is a free agent getting very little interest.

Extending windows of opportunity is always the biggest challenge facing a front office. Brady gave the Patriots a 20-year run of success. No other franchise has come close to anything like it. The Red Sox transitioned from the curse-busting group of 2004 to win three more championships with young, homegrown talent.

Betts was the best of the group. While he has won two titles in Los Angeles, the Sox have missed the playoffs in four of the five seasons since he left.

There is no playbook for moving on from a generational talent. The Patriots feel they tried to ride Brady as long as they could. He walked away as a free agent. In hindsight it’s clear they should have done more to keep him happy and around longer.

The Red Sox moved Betts before he could leave. They didn’t get enough in return. They also didn’t do enough to try to keep him. Years later they are still trying to convince a disgruntled fan base that they are willing to spend the money needed to compete with the top franchises in the sport.

In Foxborough, they believe they have a new generational talent in Maye. At Fenway, they feel their bumper crop of prospects is one of the best classes of players to matriculate to Boston in decades.

Let’s hope each team takes the necessary steps to build a roster worthy of their top talent. As everyone in New England knows, these windows of opportunity slam shut quickly.

Tom Caron is a studio host for the Red Sox broadcast on NESN.