New Delhi, Dec 16 : Former India batsman VVS Laxman believes the biggest challenge for captain Virat Kohli for the first Test against Australia is to find the right opening combination for the pink-ball fixture which begins Thursday at the Adelaide Oval. KL Rahul didn't take part in both the tour games, including the pink-ball practice game, which India played against Australia A, something which implies that the Karnataka batsman is not in the mix for the day-night Test, says Laxman. Shubman Gill and Prithvi Shaw opened the innings in the first practice game at the Drummoyne Oval while Mayank Agarwal and Gill opened the innings in the second warm-up match at the Sydney Cricket Ground. Shaw wasn't able to perform in both the warm-up matches as he returned with scores of 0, 19, 40 and 3. On the other hand, Gill played knocks of 0, 29, 43 and 65. "I think it's the batting line-up and it's the opening combination. When we see the practice games, I was surprised that KL Rahul was not playing the only practice match with the Pink Ball. That means he is not in the fray as far as the first Test is concerned, which means it has to be decided between Prithvi Shaw and Shubman Gill," said Laxman while speaking on Star Sports show Cricket Connected. Laxman also stated that both Shaw and Gill don't have the desired experience of playing in Australia. While Shaw has played just four Test matches, Gill is yet to make his debut in red-ball cricket. "Prithvi Shaw, low in confidence, Shubman Gill hasn't played a single Test match, so inexperience is there as far as the opening partner, who is going to open with Mayank Agarwal. So, that's the biggest question I feel Virat Kohli has in front of him," he said. /IANS