The Spanish defender suffered a knee injury last weekend that has since ruled him out for the remainder of the season.
Having seen his side ship three goals on their first outing without Ramis, Martinez conceded that he may now look to recruit another defender before the transfer window closes at the end of the month.
"Today we weren't good enough defensively for 30 minutes. We need to rectify that," Martinez told reporters. "Ivan Ramis's injury last week cost us today's points. That is something I need to correct."
Ramis joined Wigan last summer from La Liga side Real Mallorca.