West Brom have been beaten just three times in the league since Tony Pulis was appointed as head coach in January, and sit eight points clear of the relegation zone.
Midfielder Mulumbu feels that West Brom have performed better than their 14th-placed standing suggests.
However, with fixtures against Liverpool, Manchester United, Chelsea and Arsenal to come among their final five matches, Mulumbu has stressed the importance of West Brom not resting on their laurels.
"To be fair we deserve to finish in the first part of the table," he told Perform.
"But we need to secure our position really quick because the last five games are against the big teams - Chelsea, Liverpool and Manchester United.
"They're going to look for points to stay in the top four so we need to secure our place before this game."
West Brom return to action after the international break with a home encounter against relegation-threatened QPR on Saturday.
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