With the scores level at the Hawthorns on Saturday, Defoe grasped his chance in the absence of the injured Rafael Van der Vaart with an 81st minute strike which set Spurs on their way to a 3-1 victory.
Redknapp had insisted in the build-up to the match that the England international, who had not started in the Premier League since October 2, would not be sold in January.
And, after praising Defoe's second-half display, he admitted that the England international has been unfortunate to find himself on the sidelines.
Redknapp said: "We lost Rafael with a hamstring but Jermain has been in fantastic form. We had a reserve game on Tuesday and he got five goals against Charlton and he looked so sharp.
"Some of his play in the second half was fantastic. He has been unlucky. I can only play him or Rafa who has played well and scored goals.
"He had that run of five or six goals in five games so it has been difficult for Jermain and I felt sorry for him. I told him that but there was nothing I could do. I've got (Emmanuel) Adebayor and one to play with him."
It was a fifth successive win for Redknapp's team, moving them within two points of Manchester United, and their first in six attempts at the Hawthorns.
But Redknapp was unhappy with the way his team started the match, having gone behind to Youssouf Mulumbu's 10th-minute header.
They levelled against the run of play 15 minutes layer when Nicky Shorey's foul on Aaron Lennon resulted in a penalty and Adebayor bundled home at the second attempt after seeing his initial effort saved.
Chances were spurned at both ends before Defoe finally struck in the 81st minute from the edge of the area with Adebayor making certain of the win with his second in injury-time.
Redknapp said: "It is encouraging but we've got to realise we have to play like we did second half.
"The first half wasn't good enough and I told them that at half-time. We are better than that and I told them.
"We started poorly and didn't move the ball quickly enough. They started better than we did and went in front and there was more chance of them going two up at that time than us pegging it back.
"It looked a penalty. You may disagree with me and it looked like Shorey clipped his heels. You get that given 19 times out of 20.
"In the second half we upped the pace and our two wingers started running at people. We opened them up and should have scored a lot more goals."
West Brom have now won three and lost three in their last six Premier League matches and head coach Roy Hodgson cut a frustrated figure afterwards.
"I didn't think we deserved to lose. They had a lot of counter-attacking chances at the end," Hodgson said.
"I thought our shape, passing and movement was good but the result was rubbish."
Source: AFP
Source: AFP