redshirt
New attitude pays off for Oregon redshirt freshman Tyson Coleman, a former Lake Oswego standout
EUGENE ― Tyson Coleman stepped on the scale Sunday morning and continued to be surprised at his growth.
Oregon's redshirt freshman linebacker weighed in at 225 pounds, up from 207 at the start of the season and 199 when he first arrived on campus in April 2011.
A year ago at this time, football was temporarily taken away from Coleman, a penalty imposed by the team as consequence of his arrest in May 2011 from a minor-in-possession incident near campus.
Though redshirting at the time, Coleman was not allowed to practice during December last year, often a crucial time for development of young players. Worse yet, he was barred from traveling with the team to the Rose Bowl. (Typically, the entire team ― including walk-ons and redshirts ― travel to bowl games, even if they aren't expected to play.)
http://www.oregonlive.com/ducks/index.ssf/2012/12/new_attitude_pays_off_for_oreg.html
redshirtとは何を意味するのでしょうか。（『ジーニアス英和辞典 第４版』大修館）では他動詞で、「<大学のスポーツ選手>を１年間留年させて試合をさせない《選手資格を延長するために行なう》」という意味と、名詞で「留年選手」という意味が載っていました。また、redshirtという言葉の起源は、チーム内での練習試合でレギュラー選手の相手になる選手が赤いジャージを着ていたからだそうです。
Origin of REDSHIRT
from the red jersey commonly worn by such a player in practice scrimmages against the regulars
First Known Use: 1955 （merriam-webster.com）
また、留年選手という言葉に馴染みが無かったので、もう少し調べてみました。infoplease.comを見ると留年選手について簡潔に説明されていました。
The Question:
In college football, what is the definition of a redshirt freshman and a true freshman?
The Answer:
When a freshman athlete is referred to as being "true," it means that freshman is playing for the school during his or her first year of college classes.
When a player is given the "red-shirt" designation by his or her coach, that means he or she has participated in a college's academic year, but did not participate during that year's sports season.
Most likely a "red-shirt freshman" in college football is a sophomore in college who practiced with the team his first year, but did not play in any games (at the coach's request), or was seriously injured during his first season. The "red-shirt" designation means that that season will not count against the player's four years of NCAA eligibility, allowing him to play four full seasons.
―The Editors
Read more: The Redshirt Freshman ― Infoplease.com http://www.infoplease.com/askeds/redshirt-freshman.html#ixzz2FJYR42yY
怪我の療養、競技能力の向上など、様々な理由で大学生活の一年目を準備期間として費やし、２年目からの４年間で選手として活躍する事があるようです。一方、一年目から試合などに出る選手を、true freshman というようです。(Astroriver)
