Gamboa - an off-season arrival from Rosenborg following his exploits at the 2014 World Cup in Brazil - has only played one minute under Pulis since the Welshman replaced Alan Irvine in January.
The 25-year-old, whose sole appearance under Pulis came as an 89th-minute substitute during last month's FA Cup fixture against West Ham, was an unused substitute in West Brom's 1-0 Premier League win over Stoke City on Saturday.
Gamboa believes his size is costing him a spot in the starting line-up, with the Costa Rican resigned to leaving the West Midlands at the end of the season.
"I don't play because the boss doesn't like me," Gamboa told The Mirror.
"He has always liked these two-metre tall defenders and likes to play with four centre-backs. He doesn't like wing-backs capable of attacking.
"My style doesn't suit his style. So, I have no chances of playing.
"So, if this boss is still in charge at the end of the season, I will leave West Brom. I have to leave this club because I do know that this boss doesn't like me."
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