Neymar has scored just three goals and provided one assist in nine matches since returning from a month out with an ankle injury, and missed three clear goalscoring opportunities in Barca's 1-0 win at Espanyol on Saturday.
Alves claims recent media criticism of Neymar coincided with speculation about the player's contract and the circumstances of his transfer, which lead to Sandro Rosell resigning as Barcelona president in January amid allegations of unpaid tax relating to the signing.
Criticism of Neymar has not just been confined to the press, however, with former Barca player and coach Johan Cruyff remarking last week that the 22-year-old's arrival had destabilised the Barca dressing room.
But Alves has stuck up for his beleaguered team-mate, insisting he is being blamed for the fallout from the transfer.
"I think the criticism only started when the details about his contract emerged, before that everyone was happy with him," Alves told a press conference.
"We should not judge him on how much he cost, but on how well he is playing.
"For me now he is playing as well as he was at the start of the season. You expect that there will always be a period of adaptation when a player arrives in a new country, but he has been playing well.
"The club paid so much for him because he is worth it. People have paid more money for players that haven't been worth it."
However, Alves said he understood that Neymar was under pressure to deliver at this vital stage of the season, in which the club are fighting to win the Primera Division, the Copa del Rey and the Champions League.
"We are at the key stage of the season and it's normal that people are demanding a lot of him," said the defender.
"People are only demanding a lot of him because they know what he is capable of. And he has to keep demonstrating how good he is.
"If you don't do that in football, you take a step backwards. If today he plays 10/10, tomorrow he has to play 15/10."
Alves was speaking ahead of the first leg of Barca's Champions League quarter-final tie with Atletico Madrid, and highlighted what a difficult tie it was for his side by joking that former Real Madrid player Luis Figo had drawn the two Spanish teams together on purpose.
"Hopefully our luck will change soon because we always get drawn with the ugliest teams. But we accept the challenge, we live for the biggest challenges, that's what motivates us," he said.
Atletico and Barcelona have met three times this season, twice in the Spanish Super Cup and once in the Primera Division, with each match ending in a draw.
However, Alves laughed off the suggestion the Catalans would be content with a draw in the home leg.
"I play to win, not to draw," he said.
"No one is going to give you an easy ride, and if you want something you have to go all out for it. I will never go into a game looking for a draw, we only play to win."
Barca have confirmed that goalkeeper Victor Valdes will be out for seven months after undergoing knee surgery in Germany and, with the player set to leave the club when his contract expires in June, he has likely played his last competitive game for the Catalans.
Captain Carles Puyol joins Valdes on the sidelines, while Alex Song and Pedro have been passed fit after recovering from niggling problems.
With the exception of suspended midfielder Raul Garcia and injured right-back Javier Manquillo, Atletico coach Diego Simeone has a full squad to choose from.