After failing to achieve the same magic with the Denver Broncos than with his subsequent teams, it looks like Tim Tebow's NFL career might finally be over. On Saturday, the former Heisman Trophy winner was released by the Philadelphia Eagles and no NFL team has picked him up.

It's no secret, even to the casual football fan, that making an NFL roster is quite difficult. But it is even more of a challenge when it's a quarterback over the age of 25 who hasn't played in a competitive game in three years. That was the case for Tebow, a 28-year-old who hadn't completed a pass in a regular-season game since Nov. 2012. 

One would think that Tebow could have been a third-stringer on at least one team. He seemed to have provided a positive audition in preseason, and on a unique offense that could have used his particular skill set. He threw the ball reasonably well in preseason action, showed that he can still scramble, and posted respectable statistics. There were also clear throwing improvements from the same Tebow who often tossed wobbly passes as a member of the Broncos.

Some may call foul on head coach Chip Kelly's decision to part ways with Tebow, and the suggestion that a stint in the Canadian Football League would strengthen his chances to make an NFL team also seems to be disingenuous. But there is more to Tebow's inability to sign with a club than some think.

First off, how many teams even have three quarterbacks on their current rosters? As it turns out, there are not as many as you might think. Twelve teams have just two quarterbacks, and one of them is the New England Patriots, who faced losing their starter for the first four games. Another team that is only carrying two quarterbacks is the Jacksonville Jaguars, and when they cut their third stringer, Stephen Morris, it was the Eagles who quickly signed him. Due to limited openings, Tebow's chances to make an NFL team were stacked against him from the moment he showed up to camp.

Second, there were plenty of quarterbacks who were cut who appear to have more upside than Tebow, proving how stiff the competition is for a coveted roster spot. While the Eagles still have Morris as their No. 3, they have recently considered adding Josh Johnson, who dashed for 76 yards on seven carries in the New York Jets' final preseason game of the season. Like Tebow, Johnson is over the age of 25, but scouts have raved about his athleticism. He also was on an NFL roster in 2013, unlike Tebow. The Eagles have also considered Thad Lewis, who completed 93 passes in 2013 and was on the Houston Texans' roster in 2014. Players like Johnson and Lewis probably deserved more consideration than Tebow because of their familiarity with today's NFL.

There also might not be much room for growth for Tebow. After so many years and so much work on his throwing mechanics, NFL teams may feel that this is as good as Tebow can get, and prefer to develop a young quarterback instead. The Chicago Bears nearly cut David Fales, a quarterback they drafted in the sixth round of the 2014 draft, but elected to keep him on their 53-man roster after an exceptional performance in his final preseason game, when he completed 14 of his 18 pass attempts for 131 yards and two touchdowns. Fales has never played an NFL game, but at age 24, the Bears may think he can one day develop into a better quarterback. The ceiling appears to be higher for a player like Fales than it is for Tebow.

Many NFL fans have taken a liking to Tebow's spirit, determination and enthusiasm for the game. They also remember his accomplishments with the Florida Gators, and his underdog heroics with the Denver Broncos, all of which have made him stand out over nearly all other aspiring NFL quarterbacks. But a lack of quarterback vacancies, the depth of experienced quarterbacks competing for jobs, and NFL teams' interest in developing young quarterbacks overshadowed all of his achievements from previous years and this preseason.