The reigning Asian champions were knocked out of the Asian Champions League by their J-League foes and Nishino was downcast by the result.
"It's a great shame to have this result," said Nishino.
"Our regular players who returned for this game gave a better performance than I expected. I thought we were playing well and showed our brand of football to some degree.
"But I felt that we started losing our movement and rhythm in the second-half and gave up the goals. That was wasteful.
"Our players worked really hard but I made mistakes tactically and took too long before making substitutions," he added.
"We had many chances for our third goal but couldn't extend our lead, especially at the start of the second half.
"It's such a pity as I felt that we were getting back to our best form. It's a shame that we cannot continue in this competition and show our true Gamba style."