At the surface level, many would say that Drew Lock has gotten a fair shake in Denver since he was drafted. He was given a quarterback mentor, got a full season to show progress, and got to sit for an extended period of time in his rookie season. However, a closer look shows that Drew Lock has had as tough of an introduction into the NFL as any quarterback in the last few seasons.Drew Lock's first issue: MentorOn the surface, getting a Super Bowl MVP to mentor a newly drafted quarterback is a no-brainer. However, in practice, it did not go as planned. When Joe Flacco said he didn't view mentoring Drew Lock "as his job," it put Lock on an island.Of course, Lock was still able to watch Flacco work but there is little difference between doing that and watching tape. Also, when the mentor started 0-4, the quality of his examples was suspect.Joe Flacco focused on winning games, not mentoring rookie QB Drew Lock https://t.co/LDADzQ2oAQ pic.twitter.com/5NqV7Iok0L— Around The NFL (@AroundTheNFL) May 13, 2019Lack of preseasonsDrew Lock injured his hand before Week One in a preseason game. The injury knocked him out for the rest of the preseason and a big chunk of the regular season as he was placed on IR.Learning the basics of a quarterback's job is difficult. Learning the basics of a quarterback's job while fighting the pain of a hand injury is sure to hurt development. The resulting gaps in knowledge created in his rookie year caught up with him in the second year.This could be what happened when, after starting 4-1 in 2019, his team finished at 5-11 in 2020.Speaking of 2020, Drew Lock could not have a full preseason for the second year in a row as the preseason was basically canceled due to Covid protocols. This led to him essentially being thrown under fire in Week One with minimal work and a newly revamped offense.Roster holes in 2020In addition to Drew Lock's problems, the team at large was also facing their own difficulties. Offensive right tackle Ja'Waun James opted-out for the season and there was a new rookie center getting his very first snaps in Week One. Also, Von Miller and Courtland Sutton both essentially missed the season due to injuries. The absences left Lock to throw at rookies Jerry Jeudy and KJ Hamler. Running backs Phillip Lindsay and Melvin Gordon III were also in-and-out of the lineup.More on Broncos’ LB Von Miller suffering a tendon injury in his ankle on the final play of Tuesday’s practice that now will require what is likely season-ending surgery:https://t.co/RdgWMqcLRM— Adam Schefter (@AdamSchefter) September 9, 2020Put simply, the roster was on the rocks from the first snap of 2020.Between the lack of a mentor, the lack of a single full preseason, and the lack of a reliable roster in 2020, there is a substantial argument explaining why Lock hasn't had the best start to his career.Teddy BridgewaterNow in 2021, as Drew Lock faces down Teddy Bridgewater, with Aaron Rodgers possibly on the horizon, the time for "what could be" is rapidly turning into "what could have been" for the once exciting prospect.