Logan's costly error, with the tie finely balanced at 1-1, came when he inexplicably dropped Gianni Zuiverloon's long ball to the feet of Somen Tchoyi who was presented with a simple finish to put the Baggies in command - almost identical to the one presented to him by Manchester United stopper Edwin van der Sar 10 days ago.

But the former England coach insisted mistakes like these happen in football and rightly pointed to the impressive saves Logan made during the 90 minutes at the Walkers Stadium.

"Of course it's a mistake, everyone knows that and he knows that," said the Swede.

"That happens in football, but the third or fourth goals were worse.

"You know goalkeepers sometimes make mistakes, it was unlucky."

Asked whether Logan was apologetic afterwards, Eriksson added: "Of course. You can imagine how you feel when it's an important game, it's 1-1 when we are in the game and we have a good chance to win it.

"It happens in football, but he will not sleep very well tonight."

Simon Cox, who scored the winner that saw off Manchester City in the last round, had opened the scoring midway through the first half with a dinked finish over Logan but an own goal from substitute Nicky Shorey levelled things up after the break.

Steven Reid, Baggies captain for the night, found himself unmarked to head a third and put the game beyond the Foxes before Cox grabbed his second in style with a long-range strike in the last minute.

Eriksson said: "I think we were as good on the pitch as West Brom and that's good, we played rather good football, created opportunities, so it's a pity that we're out of the Carling Cup.

"It's even more of a pity for people who haven't seen this game who will think West Brom have cruised over us, that was not the case.

"But saying that, it doesn't really matter how good football we play if we don't stop conceding goals that easy.

"It's absolutely too easy to score goals against us. If we don't change that then we can forget about the play-offs or promotion."

The result sends West Brom, one-time winners of the competition, into the last eight for the first time since 2003.

And assistant manager Eddie Newton admitted Logan's clanger was the pivotal point in the match - 10 days after Tchoyi profited in similar circumstances at Old Trafford. "A few of the boys are thinking he's making incantations when the ball's in the air as he's coming over," Newton joked.

"But at least he's in the position, when he first joined us he wouldn't have been in those positions to take advantage of those slip-ups by keepers.

"We're just as aghast as well, we don't know what's going on, but if that keeps happening for him he might be starting week in, week out."

Newton added: "I'm very pleased, it's a fantastic result. I'm very pleased with the performance in both aspects of defending and attacking."