After boasting two one of the top defensive lines in the entire Big 12 a season ago, TCU football will have shoes to fill in 2019 upon graduating two key playmakers who likely have NFL playing careers ahead of them.So can head coach Gary Patterson -- known for his keen eye when it comes to undervalued talent -- once again oversee lesser-known players undergoing meteoric rises to the best the league has to offer?Here is a rundown of what to expect for TCU’s defensive line this fall:Key ReturneesRoss Blacklock (junior): Following a redshirt season in 2016, Blacklock started in all 14 games of the 2017 season as redshirt freshman, picking up both FWAA Freshman All-American and Big 12 Co-Defensive Freshman of the Year honors.