He played college football for the Baylor Bears, and was selected by the New York Jets in the fourth round of the 2015 NFL draft.

[2] He played football for Midlothian and was named District 15-4A Offensive Sophomore of the Year after throwing for 979 yards and four touchdowns in 2006.

[17] He led the Bears to a share of their second straight Big 12 title as they appeared in the 2015 Cotton Bowl Classic, losing to Michigan State.

[25] Petty made his professional debut on August 13, during the first preseason game against the Detroit Lions where he completed 10-of-18 passes for 50 yards.

[27] Throughout the season, Petty served as a third string backup behind veterans Ryan Fitzpatrick and Geno Smith and did not appear in any games.

[29] Due to Fitzpatrick's injury in the previous game, Petty started for the Jets just a week later against the Los Angeles Rams, where he completed 21-of-34 passes for 163 yards, a touchdown, and an interception.

"[32] In Week 14 of the 2016 season, Petty notched his first career win as a starter, throwing for a career-high 257 yards as he helped lead the Jets to a 23–17 overtime victory after trailing the San Francisco 49ers 17–3 at halftime.

However, in the second half, a lousy effort by the Jets defense led to three touchdowns in four minutes by the Dolphins spoiled Petty's contributions, eventually leading to a 34–13 loss.

[34] On Christmas Eve against the New England Patriots, he injured his left shoulder in the second quarter after tackling cornerback Malcolm Butler after he recovered a fumble by running back Khiry Robinson in a 41–3 blowout loss.

[38] During Week 14 against the Denver Broncos, Petty entered the game for two plays after Josh McCown suffered an apparent back injury.

[40] During Week 16 against the Los Angeles Chargers, Petty was held to 119 passing yards with an interception as the Jets lost 7–14.