The Japanese club eventually won 5-0 after being four goals up after 50 minutes in an outcome that Sekizuka did not dream of.
"This was very different to what I expected," said Sekizuka.
"My team was able to defuse the strong points of the Mariners and were able to use our skills to our best advantage.
"Even though we won this time we do play them again in two weeks time and we will prepare ourselves very carefully. We expect it to be a challenge. We don't feel tonight was really representative of the Mariners.
"It wasn't what we were expecting and we will expect more from them in Japan. We will continue to prepare to the best we can for the upcoming matches."