Steve McClaren admitted he was relieved to still be in the FA Cup after his QPR side came from behind to draw 1-1 at League One leaders Pompey.
Joel Lynch's 63rd minute own goal looked to have sent Championship Rangers crashing before Nahki Wells salvaged a replay for McClaren's men 16 minutes from time.
Hoops manager McClaren, part of Sir Alex Ferguson's coaching staff when Manchester United won the cup in 1999, said: "I would have settled for a replay before the game.
"The conditions were horrendous. The wind was swirling and this had the potential to be a big banana skin for us.
"Kenny Jackett has done a great job here. They are top of League One and will get promoted, no problem. They have got good players and showed that today.
"We were pleased with the first half but when we went a goal down the crowd really got behind them and our boys fought tremendously well and showed great character.
"We equalised and then it was both teams slugging it out for the winner."
Rangers, bidding for a first fourth round win in 22 years, should have taken the lead in the first half when the hapless Lynch squandered a free header.
Visiting goalkeeper Joe Lumley did superbly to tip Louis Dennis' 20-yard volley behind for a corner on the stroke of half time.
Pompey captain Brett Pitman had put a one-on-one with Lumley over the bar when Lynch sliced a clearance from Lee Brown's cross into his own net.
But McClaren's side hit back 11 minutes later as Wells tucked home from close range from a Luke Freeman corner.
The replay means 2008 winners Pompey face a hectic schedule of five games in the space of 14 days.
Jackett said: "We had a good go and ultimately we are disappointed because we got our noses in front and could not hold onto it.
"It was a tight game. We built our momentum up in the second half and got our goal.
"Their quality was there on the break, particularly in the first half and we had to be aware of it.
"It was a solid performance from us without really having the cutting edge to get a lot of shots in or people off the bench to change it.
"It was a game of very few clear-cut chances but the second half was a good performance from us.
"We were solid and competitive and we look forward to the replay now, which will be another tough game"
