Doha: A Boualem Khoukhi brace gave Qatar's Al Sadd a narrow 2-1 win at home over Al Ahli of Saudi Arabia in the first leg of their 2018 AFC Champions League Round of 16 tie on Monday.   Al Sadd started their first AFC Champions League knockout game since 2015 brightly, and made the breakthrough in just the third minute as Khoukhi got into the box after a fine exchange with Xavi and coolly slotted home with his left foot for the opener.   Despite the early setback, the visitors seemed confident of levelling the scores and came close to scoring twice in the space of one minute. However, Ahmed Suhail and Salem Al Hajri produced two goal-line clearances to deny Abdulfattah Asiri and Hussain Al Mogahwi respectively.   Just as Al Ahli looked to make their mark, Khoukhi struck again in the 28th minute, doubling Al Sadd's lead with a powerful header past Mohammed Al Owais following Baghdad Bounedjah's cross from the right.   Al Sadd thus went into the break with a 2-0 lead but a revitalised Al Ahli side emerged from the tunnel with a desire to change things around. They were rewarded just two minutes into the second half, with Mohannad Aseri heading in Amir Kurdi's cross to reduce the deficit.   That goal set the stage for a feisty second half which saw both sides carve up numerous chances but no goal materialised. Tournament leading scorer Bounedjah was caught offside on multiple occasions while Saad Al Dosari stood his ground at the other end to deny the Al Ahli forwards.   The result leaves the tie nicely poised going into next week's second leg in Jeddah's King Abdullah Sports City.