The 25-year has been criticised for his goalkeeping errors over the past few months – ever since the Champions League final against Real Madrid, that the Reds lost 3-1.
Casillas, however jumped to the defence of Karius after he had made yet another error in a pre-season friendly against Borussia Dortmund on Sunday that led to a goal.
On Tuesday, the Spain legend tweeted his own blooper reel that included errors Casillas had made in big Champions League and international matches during his career.
The World Cup winner wrote: “Behind each one of us is a person. Raise your hand whoever has never made a mistake. Learning from mistakes makes us stronger and accepting them more human. #Ialsomakemistakes.”
The Switzerland international has been on extended leave because of his involvement in the World Cup – interrupting that only to complete a £13million move from Stoke – but that is now over and the 26-year-old has some catching up to do.
Liverpool’s squad will will train in Charlotte, North Carolina, before flying to New Jersey ahead of their International Champions Cup match against Manchester City.
Shaqiri is already in New York so will meet them there but Thursday’s match, their second of three in America, will come too soon for him to be involved.
But while he gets up to speed, manager Jurgen Klopp has to get to grips with trimming down his squad.
Having added Shaqiri, midfielders Naby Keita and Fabinho and goalkeeper Alisson, the German now needs to make big decisions on who to keep, who to loan and who to let go.
Striker Danny Ings, who was left behind on Merseyside to do extra work on his fitness after an ankle problem, seems one of those players likely to be on his way out after three frustrating, injury-plagued seasons at Anfield.
Promising youngsters Harry Wilson and Ovie Ejaria have gone on loan to Derby and Rangers respectively while third-choice goalkeeper Danny Ward has been sold to Leicester.
“When all the players are back the squad is big, so it is clear they all need opportunities to play,” Klopp told liverpoolfc.tv.
“The ones who are very young, we don’t think about it; they are in absolutely the right place now and if they can play with us or the under-23s, it is perfect.
“Both is really good and we don’t have to rush that, but then we have other age groups where you think it makes no sense to show in a different league, maybe a different club in a different league, how far they are in the moment.
“Then of course, it is clear there are always requests from other clubs and we need to stay open for that.
“In the end, it makes no sense to have 35 players in the squad because developing players means they have to feel needed; they need to see ‘in this or this situation, I can play in the team’ and all that stuff.
“I am pretty sure a few things will happen, but exactly what time will show.”
The pre-season for Jurgen Klopp’s Liverpool was meant to be a time for high profile new arrivals to start feeling their way into the club, and for precocious youngsters to push for a spot in the first-team squad.
But the surprise package to emerge from the Kop club’s fixtures to date is not Naby Keita or Fabinho, Curtis Jones or Rafael Camacho – it’s the Reds’ forgotten man: Daniel Sturridge.
A player who was expected to be lined up to go out again on loan or even be sold has suddenly forced his way back into the reckoning.
“Studge” was a lethal part of Liverpool’s “SSS” strike force in 2013-14 (Sturridge, Suarez and Sterling) that almost led the Merseysiders to their first league title success in nearly 25 years.
Suarez led the goalscoring feats with 31 in the Premier League that season but Sturridge managed an impressive 21, a number which compares very favourably to Roberto Firmino’s 15 and Sadio Mane’s 10 last term.
I know it’s only pre-season but Sturridge looks back to his own self.— Kaneyy 🏴 (@Kaneyy_) July 19, 2018
Mane Sturridge Salah
Robbo Virgil Lovren TAA
In his pomp the Birmingham-born 28-year-old was just as good as those two members of Liverpool’s current “Fab Four”.
And with Philippe Coutinho now well established at Barcelona and Alex Oxlade-Chamberlain out injured for the season, there is currently an opening in that magnificent quartet.
The role requires someone like Coutinho or the Ox who can be both supplier and goal scorer – and also has the ability to step into the front line if required.
The thinking was that Lyon’s Nabil Fekir would play that role, but with his transfer falling through after a mysterious medical – and Adam Lallana still working his way back to his best following injury – Liverpool are now left searching for other options.
With around three weeks to go until the August 9 transfer window deadline, Jurgen Klopp has declared that Liverpool’s off-season spending spree is done. Even so, Sturridge could feel like a new acquisition.
Those who have watched Sturridge struggle with a catalogue of injury problems over the past three years – or his abortive loan spell at West Brom – will be astonished at this turn of events but the former England international seems to be benefitting from a fresh start.
So, you believed in Daniel Sturridge again? pic.twitter.com/OauwHcF6f8— Paul (@Kolology) July 22, 2018
There are three factors in this miraculous transformation.
Firstly Sturridge is – and long may it continue – injury-free and the rare healthy status seems to have given life to a more positive attitude.
“I’m enjoying myself and enjoying my football. I can’t ask for any more,” Sturridge told Liverpool’s official website in the USA the day after the Borussia Dortmund match, where again he was among the Reds’ best.
“I love it here. I love the lads and the banter in the group is unbelievable. I feel at home again.”
Strange thing to say as he never really left.
Each appearance so far this summer has provided a glimpse of the No15’s plentiful natural ability and predatory instincts in front of the goal – and the manager is noticing.
“The second-half without Daniel would have looked completely different,” Klopp said on Sunday after the 3-1 loss to the Bundesliga side.
With the returned fitness has also come a change in attitude.
The disastrous loan spell at the Baggies, where he played just six games as the Midlanders were relegated, has sharpened Sturridge’s survival instincts and more than ever he wants to be part of Klopp’s project.
“It was important for me to get my head in the right place and evolve as a person,” admits Sturridge.
“I had things that I needed to sort out with my family and things like that.
“I’m just happy to be back and to push myself and be part of the group again.
“I learned a lot watching the games the boys were playing in and also being away and being in a different team’s environment and seeing how they work too.”
Sturridge on Keita:— Henry Jackson (@HenryJackson87) July 23, 2018
“I haven’t seen a midfielder like him for a while, he is something different. It’s crazy. The things he can do with the ball – he can defend, he can pass, he can dribble, he is fast, he is strong. He has got everything."
Be excited, Reds.
The second factor is his on-field role seems to be changing.
Taking his cue from the ever revolving fab four – Studge has placed greater emphasis (self-imposed) on dropping deep to provide the goalscoring chances he used to finish.
In the Dortmund game alone he laid on superb chances for young strike partners Sheyi Ojo and Dominic Solanke – that Messrs Salah, Sane and Firmino would have gobbled up.
“I’m probably just doing more,” admitted Sturridge candidly.
“It’s important for me to try to get involved.
“Playing on the shoulder is what I like to do but it’s also important to come and get involved and get in and around the opposition’s No.6.
“It’s adding more strings to my bow and giving the manager more options if he needs to play me deeper.
“But wherever I play, it doesn’t matter – it’s just important to get the minutes.”
Despite adopting more of a playmaker role, Sturridge hasn’t lost his goal-poaching instincts and already nabbed three this season – two against Chester and another sweetly struck finish against Blackburn.
The third reason for Sturridge’s pre-season boost is his immediate understanding and rapport with Keita, a key part of Klopp’s plans.
The pair seemed to have developed an instant telepathy with Keita supplying some superb balls to a perfectly placed Sturridge and vice-a-versa.
Klopp must be tantalized to see how this partnership could develop.
These three factors plus the late returns of some of the Reds’ World Cup participants, opens a rare door for Sturridge.
The Premier League campaign gets under way in three weeks’ time when the Reds take on West Ham at Anfield.
With youngsters like Solanke, Divock Origi and Ojo not taking their chance to cement a spot, Sturridge is in prime position to be in that playing squad – even (depending on availability) in the starting XI.
It would then be up to him to hold his place.
But Sturridge is not focusing just on the Hammers – he is thinking long-term.
“My ambition is to train hard and work hard,” he concluded.
“There are a lot of games during the season so it’s about giving your all when you get your minutes.
“We want to win trophies and we want to be successful. It starts now and it’s a long season.
“It doesn’t matter whether you play the first game or the 50th game – as long as you’re involved in the journey that’s all that matters.”
And at the moment that is a journey that increasingly looks to involve Daniel Sturridge.