Strauss\' 100th Test will be overshadowed by the controversial absence of the Pietersen for the deciding match.
London: Captain Andrew Strauss' 100th Test for England at Lord's this week will be overshadowed by the controversial absence of the team's most dynamic batsman Kevin Pietersen for the deciding match against South Africa.
England, who trail 1-0 in the three-match series, must win to retain their status as the world's number one-ranked team.
They will have to do without South Africa-born Pietersen, 32, who was dropped at the weekend and has since admitted sending "provocative" text messages to members of the opposition.
While Pietersen has now apologised, Strauss feels "let down".
Strauss backed the decision to remove Pietersen, who scored an exhilarating 149 in the drawn second Test at Leeds, and believes "underlying issues on trust and respect" must be addressed if he is to return to the side.
"It's going to be testing," Strauss told reporters on Wednesday at Lord's. "As England captain things are sometimes thrown your way in a way that you have not necessarily been prepared to deal with.
"We have to look at the best way of moving forward and quite frankly for the next five or six days it (the Pietersen issue) is not going to be in the forefront of my mind. I have to concentrate on my batting and leading the side out in the middle and we will address these issues come the end of the Test match."
South Africa have outplayed England in the first two matches of the series and thoroughly deserve their 1-0 advantage heading to Lord's.
Strauss hoped the situation the hosts' find themselves in could work in their favour.
"Adversity can bring you slightly closer together. We have seen that before with us on a number of occasions. That is going to be the test of us this week," he said.
"I have got every confidence that we can win this Test. This is a great opportunity for us to show some strength and resolve and come through."
Playing 100 Tests would be a proud moment for Strauss but he said he would not dwell on the achievement as it could serve to be as much a distraction as the Pietersen issue.
South Africa have everything to gain from a strong performance at Lord's and another day of being quizzed by reporters over the Pietersen row has left skipper Graeme Smith perplexed.
"I find it quite amazing that it's still going on and that it has reached this point," Smith told reporters. "In our dressing room it's something that's hardly been discussed except the amount of time and coverage that it's getting.
"But obviously Kevin feels that he's done something wrong and he has apologised for that.
"From our perspective it's just been so overboard really. I can't believe it's still carrying on."
Like Strauss, Smith will savour a career highlight when he becomes the most experienced test captain ever at Lord's. His 94th Test as captain will be one more than Australian Allan Border.
"To be able to last as long in the job as I have is a proud moment," Smith said.
"To have had the support of my team mates through all those years in different times is a special thing. I definitely don't see myself in the echelons of Allan Border, Clive Lloyd or Steve Waugh, Mike Atherton or whoever. I've always tried to be the best I can be. I feel blessed to have had the opportunity to captain South Africa 94 times."
If the Proteas avoid defeat at Lord's, it would not only take them to the summit of the rankings but it would also end England's impressive streak of seven straight test series wins at home and extend the Soutth Africa's six-year unbeaten run in away Test series.
South Africa, who won the first Test at The Oval by an innings and 12 runs, are expected to name an unchanged team for the third consecutive match. England are likely to make two changes with Jonny Bairstow playing instead of Pietersen and off-spinner Graeme Swann being recalled at the expense of either Steven Finn or Tim Bresnan.