The pair were both on the scoresheet as the Tigers drew 2-2 with West Ham United on Monday night and Egyptian ace Elmohamady believes they will only improve further as the season progresses.
Club-record signing Hernandez, who joined from Palermo for £10million, was the star performer for Hull on the night and his display was not lost on Elmohamady who felt the Uruguayan could have netted twice on debut.
"It was a great header. The finish was class. He got the ball perfectly and he was also unlucky not to score a second (when hitting the bar)," said Elmohamady.
"I thought he also looked fantastic on the ball. He looked assured and wanted to run at the opposition. He went past a lot of them. That is a good sign.
"We've already seen what he can do and what a great player he is. He's a very good international player, he knows how to finish, that's for sure. He looks sharp. He doesn't speak English yet but he will learn.
"The new lads are absolutely class, as you can see from Diame and Hernandez scoring on their debuts in front of the fans.
"We're looking to play really good football this season and the new signings will only lift our confidence."
Hernandez and Diame will get the chance to contribute to Hull's current record of one win, two draws and a loss when they travel to bottom-placed Newcastle United on Saturday.
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