Warren Gatland has urged Wales to seize their opportunity against South Africa on Sunday as Wales attempt to reach the Rugby World Cup final for the first time.

Having taken over in 2007, Gatland is in his final two weeks in charge of Wales before returning to New Zealand and the Chiefs. It is the second time he has reached the semi-final in his third World Cup and, after the narrow defeat against France in 2011, he believes they have never had a better chance to win the tournament.

“We have got a pretty clean bill of health and you get these opportunities once in a lifetime potentially,” Gatland said. “You have to grab it with both hands and make the most of it. It is important that we prepare well this week and let the occasion take care of itself The motivation for the staff who are leaving and players who will have their last opportunity is to leave nothing on the table and make the most of the chance, having no regrets.”

Wales are the only semi-finalist to make it through to the last four narrowly with Gatland admitting that, overall, he was disappointed with the performance against France while again admiring the character of his side to once again come from behind to win.

“It is now about looking forward to the semi-final,” he said. “We are familiar with South Africa and have had some close encounters with them in recent years. Their line speed was good against Japan and they will kick a lot. They won the Rugby Championship and we will be up for what we know will be a tough game. We have lost to them narrowly in the last two World Cups and I think Sunday will be close as well.

“We have to get ourselves mentally and tactically right this week. The players are not going to get fitter or stronger by being in the gym: it’s pretty important that we manage them because there will be no lack of adrenaline.”

The sense of injustice France felt as they returned home after losing to a late try they disputed was aggravated by a photograph published online of the match referee Jaco Peyper posing with a group of Wales supporters in Oita and simulating the elbow on Aaron Wainwright that prompted him to send off Sebastien Vahaamahina. World Rugby is investigating. The second row, meanwhile, announced his international retirement on Monday.

“He [Peyper] has had his 50th cap and is posing with a few fans and making a bit of a joke about an incident in the game,” said Gatland. “How people interpret that is up to them, but the way things are and how pc everyone is now, people like to make mountains out of molehills.”

Such is the strength in depth that Wales have developed since the last World Cup, when they were eliminated by a late South Africa try in the quarter-final, their opponents in Sunday’s semi-final, that they are sending for a back to replace the back rower Josh Navidi who suffered a tournament ending hamstring strain against France on the weekend.

Wales have ample cover for Navidi, a flanker who has established himself at No 8 in the World Cup, but their centres Jonathan Davies and Hadleigh Parkes are carrying injuries. Gatland has therefore decided to call up the Cardiff Blues wing Owen Lane who was part of Wales’ pre-tournament training squad. The 21-year-old, who scored a try on his Test debut in August’s warm-up defeat to Ireland in Cardiff, is also comfortable at centre.

Wales arrived here on Monday night after being held up in traffic with roads near their hotel closed ahead of a ceremony on Tuesday to mark Emperor Naruhito’s ascension to the throne. A number of dignitaries, including Japan’s prime minister, Shinzo Abe, are staying at Wales’s hotel, the one vacated by Japan that morning, with everyone entering the buildings having to go through airport-style security.

“We have a couple of challenges in the next few days with the prime minister being here,” said Gatland. “We had to come in a separate entrance and there are metal detectors with a couple of hundred security guys around the hotel. We don’t know how our bus is going to get in or out so we have a few challenges to work through.”