In a post-match chat with reporters, the Lankan captain said his team was not shamed "because reaching the semifinal was the first target for the players".
Mathews said 181 was an inadequate score against a strong Indian batting line-up.
"We needed at least 250 for a fight, but nothing went in our favour today. The toss proved to be very crucial," the 26-year-old captain said.
Mathews refused to criticise Lasith Malinga for failing to produce anything special on a big day.
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Losing wickets at regular intervals hurt Sri Lanka, said Mathews.
"First of all, Dilshan's injury early in the innings (fourth over) really hit us. He was batting well in seaming conditions. Then we lost wickets and could not rebuild our innings. There was no momentum. India's bowlers did a good job," he said.
Mathews said Sri Lanka were not shamed in losing another semifinal match.
Mathews said his team had prepared well against India.
"We had our chat and we knew they were very strong. We had to play very good cricket and we couldn't do that against India. I really can't figure out why (we play badly against India)," Mathews said.