Auckland - Springbok lock Bakkies Botha has been given an ultimatum to prove his fitness or head home as the world champions get set for their final Pool D match against Samoa in Auckland on Friday.WIN a pair of the new adidas rugby bootsWIN a Rugby World Cup ballBotha has been struggling with acute tendonosis on his Achilles heel since the beginning of the tournament, and missed the game against Wales as a result, but returned for good performances in the big victories over Fiji and Namibia in the last fortnight.But now, with the playoffs looming, coach Peter de Villiers has told his lock he needs to be fit before the playoffs or head home.De Villiers said he wanted a fully-fit squad ahead of the game against Samoa, and had already decided to rest captain John Smit and play fiery hooker Bismarck du Plessis in his placeVictor Matfield will return to the side after a calf injury ruled him out of the last two games, and is likely to captain the side.But Botha remains the main concern for the side as they move into playoff mode ahead of the Samoan game."Bakkies is a worry at the moment. I don’t think Bakkies is where I want him to be, even though he may be where he wants to be," De Villiers explained."Then again, he is such a valuable player for the team, but a 90 percent fit Bakkies won’t be good enough to play for the side, he needs to be 100 percent."He will be in doubt for Samoa. When he injured himself the other day, I really felt for the man because he worked hard to get fit again."In rugby when you aggravate your injury again, it takes longer to come back. We will make a decision on Bakkies, but we will be led by the medical team and by Bakkies himself."I can’t say if we will decide to send him home, we can’t keep any player here after this week if he isn’t ready to go."De Villiers said he needed to give Du Plessis a start so that the entire squad had started one game at the World Cup and the management would finalise the team on Saturday while the players were given time off until Sunday night."We will sit down today and we will know after today who will start this weekend, because what Samoa will offer, will cause us to make some changes," De Villiers said."One thing I can tell you today is that Bissie (Bismarck du Plessis) will also start. We need to give him that start so that he can feel comfortable in his mind and John (Smit) needs to rest."John had a tough time over the past few weeks. He went on like Duracell batteries, he just keeps on going. Not that he squeals, but I have to manage him too."Bismarck will also need some guys around him to enhance his talents and I think we have the right players there. We’re looking forward to this game, but we’re also looking forward to the challenge they bring us."The Boks will begin their training for the game on Monday with the team announcement set for Tuesday.