Pizzi's men fell to a 2-0 defeat in their away leg, courtesy of first-half goals to Stephane MBia and Carlos Bacca, and club president Amadeo Salvo lambasted referee Damir Skomina and his team, which consisted of three Slovenian officials, including central ref Skomina.
Salvo lamented UEFA's usage of three officials from the southern central Europe nation, but Pizzi was not as blatant in his criticism - but did claim the result might not have been a fair reflection of their efforts.
"I'm not going to publicly criticise him," Pizzi said of Skomina.
"I think the images speak sufficiently for themselves, it's clear that everyone saw what happened.
"I'm proud of team, despite the result, which doesn't accurately reflect what happened on the pitch.
"We leave here with the pain of defeat, but knowing that we can turn it around.
"As I said before, if there was anything I could say that would change the result, I would. I can't find any appropriate statement, so I'll remain silent."
Valencia had big appeals turned away for offside for MBia's opener from a set piece, although they could have no complaints with the second goal - as Bacca and Vitolo cut the defence open before the former finished strongly.
"The players are livid over the situation leading to the (MBia) goal and the result, but the group has shown me that despite many difficult occasions they have always surprised me and risen up to the occasion, this is just one more occasion," Pizzi said.
"We're optimistic that on Thursday, we'll have a game like we did against Basel."
Pizzi's men arrested a 3-0 first-leg deficit to beat Basel in their quarter-final tie, pulling out a 5-0 victory after extra-time.
The Valencia boss said he felt his side had control of the first leg prior to MBia's 33rd-minute opener, and believes they can do likewise in the second leg.
"We were gutted following Sevilla's goal, because we were dominating the match and possession," Pizzi said.
"We felt comfortable on the opposing pitch, but they scored two goals in moments of confusion.
"When you feel you're doing things well, then concede and lose, it's difficult.
"In the second half, we were looking to score and we took risks, but we had our chances and we are hopeful (in the second leg)."
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