United are approaching their second season under head coach Marcelo Bielsa without the services of Swedish international Jansson who Leeds were happy to sell to Brentford for £5.5m after a break down in the relationship between the club and the player.
Hernandez admitted he was "not happy" with the departure of the centre-back but the experienced Spaniard is hopeful that Jansson's void can be filled by other players with the 34-year-old focused on the future and not the past at Leeds.
"I lost a team-mate and a friend but this is football," said Hernandez about Jansson's departure.
"This can happen. Teams change players. I have lived through this a lot of times in my career. This is football.
"Obviously this is a big loss for us but other players come. Obviously I am not happy because we lost him. But this is football.
"I don’t think too much about it. The most important thing now is the players who are here and who play for Leeds United next season."
Hernandez is among a squad of 16 Whites players to have flown out for United's pre-season tour of Australia which begins with Wednesday's clash against Manchester United in Perth (kick-off 12 noon BST).
Next season's objective is then ultimately to finally join the Red Devils in the Premier League after what will be a 16-year absence.
Hernandez is hopeful Leeds can atone last season's near miss with the Spaniard praying for better luck on the injury front after United's squad was ravaged by injury problems last term.
"We want to fight to get into the Premier League again," said Hernandez.
"We need to be 100 per cent from the first day.
"We hope this season we don’t have too many problems with injuries because last year we had pretty bad luck in this part of the game.
"We work from the first day for this. We want to put 100 per cent in. We need all the players.
"Now we have two or three injured but we hope they come with the group for the start of the season."
Defender Luke Ayling is missing the Australia tour having suffered a kick in training while Tyler Roberts underwent minor knee surgery in the summer.