Playing his fifth match today as he played three in the qualifiers, Amritraj lost the gruelling battle after two hours and 29 minutes.
Amritraj made a good comeback in the opening set after dropping his serve in the very first game as he took a 5-3 lead after two breaks.
Eventually, the set was stretched to the tie-breaker and Soeda, a semi finalist here last year, won it comfortably, conceding just two points to him.
However, Prakash cameback strong in the second set, raising his game by several notches. He stroked well and vollied beautifully.
His double-handed backhand strokes and passing shots stood out. He broke the Japanese twice -- third and ninth games -- to take the set in 43 minutes.
The third set was fought fiercely but Soeda's experience counted. After getting a break back in the eight game, Soeda handled crucial points better and Amritraj succumbed to over aggression.
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In another match, 23-year-old Slovenian Aljaz Bedene (ranked 86) caused a flutter by upsetting sixth seeded Robin Haase (ranked 56) of the Netherlands 7-5 6-3.
Trading breaks in the first two games, Bedene broke Haase in the 12th game for the set and then kept up the momentum to finish the match with an eighth game break.