Herndon chose to play for the San Francisco State Gators, as it would allow his mother to watch his games.
[4] He got his season high of 17 points to go with a team-high five rebounds, two assists, and two steals in a win over Cal State Dominguez Hills.
[5] In his final year with SF State, Herndon tied his college career-high of 21 points to go with six rebounds in 46 minutes as they lost in triple overtime to Dominican.
In 2016, he won first place in the Manila Red Bull King of the Rock qualifier, beating out retired former PBA MVP Willie Miller.
[16] Victoria's Sports ended the conference with a win over the Blustar Detergent Dragons Malaysia, in which he had a double-double of 19 points and 13 rebounds.
[22] In that Game 2, he had two clutch offensive rebounds to bring his total to 13 boards to go along with his 13 points and two steals as the Skippers moved on the semifinals.
[27] His father surprised him and flew to Manila to watch him play, motivating him to debut in a win over Alaska with nine points and seven rebounds.
[33] To begin the 2019 season, Herndon scored a career-high 16 points as he stepped up for the injured Paul Lee, but his efforts were not enough as they lost to the TNT Katropa.
[42] In Alaska's final game of the elimination round, he produced 14 points and seven rebounds against the NLEX Road Warriors as they finished with a record of 7–4.
[44] After starting the 2021 Philippine Cup 0–2, the Aces got their first win of the season against the Phoenix Super LPG Fuel Masters, with him contributing 13 points.
[47] Alaska then started the Governors' Cup with a win over the NorthPort Batang Pier as he scored 13 points and the go-ahead jumper with 30.1 seconds remaining.
[48] A day after it was announced that this season would be Alaska's last, he had nine points and a PBA career-high 14 rebounds in a win over the Rain or Shine Elasto Painters.
[51] On June 6, 2022, Herndon signed a one-year deal with the Converge FiberXers, the new team that took over the defunct Alaska Aces franchise.
[58] In the Commissioner's Cup, he had 11 points and six rebounds in 30 minutes as he stepped up for the injured Chris Ross in a win over the Batang Pier.
[60] As of the end of 2023–24 season[61] Herndon's father Robert Sr. is three-fourths Filipino who traces his roots to Mactan, Cebu.
[62][9] His father is a police officer in Vallejo, California, and member of the SWAT team, while his mother is a real estate agent.