Given that teams no longer keep third-string QBs on the active roster it is not a bad idea for them to get playing time in a developmental league.
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en.wikipedia.org])
"Perez was not selected in the 2018 NFL Draft, however, he was invited to attend rookie mini-camp for the Los Angeles Rams. He officially signed with the Los Angeles Rams as an undrafted free agent on May 14, 2018. Perez participated in Rams training camp and saw his first pro football action during the Rams' final preseason game on August 30, 2018 at New Orleans. Playing the entire second half, Perez completed 8-of-15 passes for 43 yards with an interception as the host Saints defeated the Rams 28-0. He was waived on September 1, 2018 and was signed to the practice squad the next day. He was released on September 18, 2018.
After being waived by the Rams, Perez signed with the San Antonio Commanders of the new Alliance of American Football. On November 27, he was drafted in the first round, fifth overall by the Birmingham Iron in the AAF's quarterback draft."