"We've lost some key players at the wrong time, Kaboul, Dawson and now Assou-Ekotto," Redknapp told Sky Sports News.
"Three defenders look like they're out for the rest of the season so it's been difficult.
"No excuses. We've got four games to go. We can still do it. We've got to win four games. We've got to go on a good run now."
Tottenham currently sit in fifth place in the Premier League and face a four-way battle for third with Arsenal, Newcastle, Spurs and Chelsea.