Ochieng opened the scoring in the 11th minute, converting a Carlos Soler assist, before teeing up Yangel Herrera for Real Sociedad's second and later supplying the pass that let Luka Sučić complete a 2-3 win with a 90th-minute winner, finishing with a goal and two assists in what was widely rated as the man-of-the-match performance.
It capped a display that justified Pellegrino Matarazzo's decision to name him in the starting line-up.
The 23-year-old's route to LaLiga began in his native Nairobi, where he grew up watching every Cristiano Ronaldo match he could find on television. At 17 he left Kenya through a crowdfunding arrangement, with his family charged €1,200 a month for the chance to pursue a professional career in Spain; when a payment fell behind schedule, the agency responsible for him abandoned the arrangement and put him out on the street.
It was at that point that Maspalomas, a club in Gran Canaria, stepped in, with former Las Palmas players Javi Martel and Carlos Gaumet helping to facilitate his move there and his subsequent progression into Real Sociedad's system.
Ochieng was one of last season's standout performers for Sanse, Real Sociedad's reserve side, in helping the team retain its place in the Primera Federación with nine league goals — form that earned him a first-team squad number for this campaign.
He made his senior and LaLiga debut in February, fittingly against Elche at Anoeta, and added two further substitute appearances before the end of last season. His only previous involvement this term had come in Real Sociedad's 4-1 defeat at the Santiago Bernabéu.
Handed a rare start by Matarazzo at the Martínez Valero, Ochieng repaid that trust in full, playing every minute of the match including the final half hour with ten men following Jon Martín's red card. His performance offered Real Sociedad a timely reminder that their squad depth extends well beyond the established regulars who began last season's campaign, and gave Matarazzo a genuine selection dilemma to enjoy heading into a congested fixture schedule.