Eighth seed Nick Kyrgios was a surprise casualty at the Malaysian Open as he was knocked out in straight sets by Marinko Matosevic.
Highly rated Australian teenager Kyrgios was unable to assert himself on proceedings and was beaten 7-6 (7-4) 7-6 (7-3) by his more experienced compatriot Matosevic.
Matosevic did not face a single break point throughout the match at the ATP 250 hard-court event in Kuala Lumpur, while Kyrgios saved five.
The 29-year-old required two tie-breaks to overcome Kyrgios, and will now face Go Soeda - who defeated fellow Japanese Kento Takeuchi - in round two.
The only other seed in action on Tuesday was Pablo Andujar, and the seventh-seeded Spaniard cruised through against Gregoire Burquier 6-2 6-4.
Bernard Tomic's disappointing run continued as he fell at the first round for the third time in the hard-court season.
Having exited the Cincinnati Open and Toronto Masters at the first hurdle, he again tasted defeat as Pierre-Hugues Herbert prevailed in a deciding set tie break, the Frenchman winning 6-4 3-6 7-6 (9-7).
Jarkko Nieminen was not troubled, though, as he came through in straight sets against Philipp Oswald.
Tuesday also saw a 6-4 3-6 7-6 (7-5) win for Philipp Petzschner over James Ward to set up a match with second seed Ernests Gulbis, and Rajeev Ram will face top seed Kei Nishikori after coming from a set down to beat Omar Jasika 4-6 7-5 6-3.