The 21-year-old, vying for a place in the first of two Tests starting in Abu Dhabi from Monday, hit 66 in a Pakistan ´A´ score of 230-4 in reply to South Africa´s 354-8 declared on the second day of the three-day match at Sharjah stadium.[break]
Pakistan needs to select three players from this tour match to add to the 12-man squad announced for the two-Test series.
The second Test starts in Dubai from October 23.
But Shahzad´s rival for the opening slot, Shan Masood, also scored an attractive 50 in a stand of 106 for the first wicket before both retired to allow others a chance to gain practice.
Ahmed has played 27 one-day and 15 Twenty20 for Pakistan since 2009 and is tipped to make his Test debut in Abu Dhabi.
South Africa´s four-pronged pace attack led by world´s best Test bowler Dale Steyn toiled hard in the heat. Of the pacemen only Morne Morkel managed a single wicket.
Steyn and fellow new ball partner Vernon Philander bowled 26 overs between them but were unable to separate the Pakistan ´A´ openers.
Pakistan´s one drop batsman Azhar Ali also notched a sedate 54 while Asad Shafiq, also fighting to keep his Test place, was unbeaten on 32 at stumps.
South African spinners Robin Peterson (1-42) and Imran Tahir (0-34) bowled tight but failed to extract much spin out of the pitch.
The two-Test series is expected to be dominated by spinners, with Pakistan likely to enter the first Test with off-spinner Saeed Ajmal and two left-armers in Abdur Rehman and Zulfiqar Babar.
Brief scores: South Africa 354-8 (J. Kallis 70, A. Petersen 58, AB de Villiers 58, Hashim Amla 50, JP Duminy 49)
Pakistan ´A´ 230-4 (Ahmed Shahzad 66, Azhar Ali 54, Shan Masood 50)
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