The 23-year-old from Madhya Pradesh rallied to grab the first two games and emerged victorious after his opponent Liew retired in the third game due to a shoulder injury with the scoreline reading 12-10 12-10 3-3 in the Indian's favour.
It was a case of being third time lucky as Sourabh, who had ended runners-up at Belgium and Poland international challengers, finally crossed the finishing line after spending almost a year on the sidelines due to elbow and knee injuries last year.
Sourabh started off well in the opening game and was leading 5-3 at one stage but Liew soon turned the tables with a five-point burst to lead 8-5. But Sourabh kept breathing down his neck and at 7-10, reeled off five straight points to grab the first game.
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In the third game, after an initial battle, Liew retired at 3-3 owing to a problematic shoulder.
(REOPENS FGN 7)
Talking about his injury-plagued phase, Sourabh said: "It has been a tough phase, I guess injuries are always difficult. Actually in 2014, I was in good shape, I was playing well but I could not win as I was cracking in crucial moments.
"I did play one tournament in June at Hyderabad All India ranking and reached the finals. I finally made a comeback in November and also reached the finals at TATA Open in December last year.
"This year I didn't get to play too many tournaments. But after reaching the finals at Belgium and Poland, I was gaining in confidence. If I could have played more events then probably I could have won the titles," he added.
"I was in top 30 in 2015 March but suddenly my ranking dropped to 190 and that is the biggest hindrance, if I could have played I could have done better," he said.
"I'm concentrating on the Grand Prix and Grand Prix Golds now. I am playing Bitburger Open next. I have to get into the top 40 as soon as possible to get entry into superseries event.