The Romania international joined Sam Allardyce's side in May on a free transfer from Ukrainian champions Shakhtar Donetsk.
However, the 32-year-old has made just one appearance this season, which came in their 2-1 League Cup success over League Two Cheltenham Town last month.
Still, Rat - who is expected to feature for Romania in their World Cup qualifier against Hungary on Friday - understands why he has yet to make an appearance in the league.
"In principle, West Ham finished the last season well," he told HotSport.ua.
"The manager decided to leave Joey [O'Brien] on the left flank in the opening rounds of this league season.
"Even before the start of the season Sam Allardyce told me that in the opening rounds he would not field me in the starting line-up.
"This is normal. He wanted me to feel the atmosphere of the English Premier League - it's a new league for me and a totally different level.
"The coach explained to me that I should first get a feel for the English Premier League, and then he will play me."