Spain took a 1-0 lead in the five-match tie.
Virtually written off even before the start, the hosts were handed a major boost before the match as Spain's star player Rafael Nadal pulled out due to a stomach bug with Feliciano taking his place.
Ramanathan, who was scheduled to face the might of the 14-time Grand Slam winner in the first singles contest of the tie, seemed to be boosted by the prospect of facing a lower rated opponent and fought bravely before going down 4-6, 4-6, 6-3, 1-6 in two hours and 15 minutes at the R.K Khanna Tennis Stadium here.
Playing in his second Davis Cup tie, Ramanathan, who had made his debut for India earlier this year, faced a stiff task against Feliciano, who is placed 26th in the world rankings.
The 203rd ranked Indian started on a positive note, holding his serve before putting pressure on his opponent's serve in the second game.
The first set witnessed a lot of long rallies as both players fought fiercely for each point. Although Feliciano was clearly the better player, Ramanathan tested him on several occasions with his excellent placements.
The Spaniard however, claimed the advantage when he broke Ramanathan's serve in the fifth game. He almost clinched another break of serve in the seventh game as well before the Indian fought back to hold serve.
The proceedings thereafter went with the serve as Feliciano took the first set to go into the lead.
Feliciano started the second set on a superb note, breaking Ramanathan's serve in the very first game. He put pressure on his opponent's serve in the seventh game as well, but the Indian saved a break point before holding serve with a powerful ace.
Despite losing the second set as well, Ramanathan was in no mood to give up.
The third set went with the serve before Ramanathan, who was struggling in the hot and humid conditions, required a medical time out after the fifth game.
But the 21-year-old from Chennai shrugged it off and took the lead by earning a break in the eighth game.
He then held his serve in the subsequent games to take the set.
If that gave rise to hopes of an upset win for Ramanathan among the sizeable home crowd, they were dashed with Feliciano outplaying the local player in the fourth set to seal the issue.
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