Fast-forward a decade, things look a little different for the now 30-year-old defender – a free agent since leaving Rotherham in July last year following their relegation from the Championship.
"How I've been? Okay," Blackett tells Tribalfootball partners Flashscore. "It's not been easy by any means, it's something which I've not had to deal with in my career before. Some days better than others.
"But I'm just getting through – staying fit and training. Just keeping on top of things and doing what I can do to be ready when the right opportunity comes.
"It's about waiting for the right fit now. There's been some interest at different times, but it's not really been right for me."
Earning Van Gaal's trust
Blackett joined United at the tender age of eight and had a plethora of legendary defenders to look up to at Old Trafford, such as Rio Ferdinand and Nemanja Vidic.
The towering duo won nine major honours together, including five Premier League titles, but their departures paved the way for Blackett to rise.
His role was facilitated by stern coach Van Gaal, who gave Blackett a hefty amount of support and confidence after his first-team promotion.
"He was strict in his approach," Blackett said of the Dutchman's style. "He was direct, and he said what he wanted and how he wanted things to be done. It was clear outlines and there was no confusion with that.
"If you were doing what he asked, he was happy and if you weren't then he would let you know.
"He was great for me. He obviously had trust in young players and gave you that confidence by giving those outlines and what he expected from you. That's what you had to focus on, and that helped me at that time.
"He was a manager who gave me an opportunity, and I have always praised him and thanked him for that."
Blackett only made 11 appearances for United before leaving permanently for Reading in 2016, and his stints at both clubs exposed him to some serious talent.
"I've played with some very big names. Paul Pogba for me (was the biggest talent). He's obviously going through some stuff recently but I'm sure when he does come back he'll get back to the level he should be at. He definitely stands out.
"Michael Olise as well, now at Bayern," he also noted. "I think those two for me are probably the standout players that I'd seen on a consistent basis doing it at the top level."
It also wouldn't feel right not to discuss record goalscorer Wayne Rooney, who was winding down his 13-year tenure at the club during Blackett's time there.
For Blackett, he says the England legend set the standard as a captain and gave him and fellow younger players a professional path to follow.
"Wayne was one of those leaders I would say (leading) by example on the pitch. The way he trained and played, he always set high standards," Blackett recalls.
"It wasn't necessarily so much as to what he would say, but how he would approach training and games.
"So, if you see your captain Wayne Rooney training as you should train and playing with intensity and aggression, it's something which you look up to and follow."
Man Utd's woes
The tail end of Rooney's spell at United brought with it challenges from fluctuating league form and a revolving door of managers, which has been the case since the great Sir Alex Ferguson's departure in 2013.
Such is the case this season, with United languishing down in 13th place and on their second manager of the season with Ruben Amorim at the helm in place of Erik ten Hag.
As a boyhood Manchester United fan, Blackett says the signs were evident dating back to when he was at the club but believes marks of improvement under Amorim are there, and he needs time to deliver.
"It's a struggle. It's going to be a struggle. It was a struggle the years back when I was there with Van Gaal," Blackett admits.
"Everyone thinks it clicks into place, but it doesn't. There needs to be time and a level of standards and consistency that players and staff all have together.
"Despite the recent results, I like the new manager (Amorim)," Blackett added. "I like how he approaches things and how he comes across. He said at the start when he came in that it's going to take time. I think it is literally that.
"As a lot of things in life, things sometimes get worse before they get better and I think that's the stage they're at now.
"But it's where you have to endure, you have to go through that because I think if they stick with him, I think they'll be able to see the changes in the way of playing and the standards he's trying to implement at the club.
"I think you see it in glimpses. There have been certain games like the Liverpool and Arsenal games in particular, you see that there is something there. But as I said, it's the consistency right now that is missing."
Faith in Rashford revival
One of those in the United squad who are ensuring the biggest challenges is Marcus Rashford, who now at 27 should be the club's figurehead and Amorim's go-to forward.
Yet things couldn't be more difficult for him with problems on and off the field, including big dips in form over the last few seasons, to the point where speculation of an exit is rife.
"With Marcus, he was quite a few years younger than me when we were coming through (at United) so we never played together," Blackett said of Rashford. "I was always aware of his talent, and I had obviously seen bits in the younger age groups.
"But we never actually got a chance to play together. From what I had seen when he was younger – maybe a few seasons ago he was able to replicate that and show his true potential and his level.
"It never surprised me that he would get to where he's got to."
Asked if he envisages a road back for Rashford at United, he added: "Yeah, I do personally. When his head is in the right space and he's performing to the level we all know he can perform, he's still one of the best players in that team, if not the best player in that team.
"But it's always dependent on the player, dependent on where his mind's at, where his head's at, where he sees himself.
"He has to know that for himself – as has been widely publicised – if he wants that new challenge, which may be somewhere else.
"Good luck to him. It's always down to the player and what is right for them. But personally, I think he's still got a lot to offer United or any team he may go to."
'Never say never' on Forest
While Blackett's beloved United remain in limbo, the opposite can be said of another one of Blackett's former clubs Nottingham Forest, who have arguably been the story of the season so far.
Forest are third in the Premier League on 44 points, six off table-toppers Liverpool and only level with Arsenal on goal difference.
It marks a tremendous campaign that few would have predicted back in August and Blackett, who spent a season at the City Ground, puts their mid-season success down to a new-found streak of consistency.
"Again, that word of consistency. Usually with Forest, we always see them change a lot of players – players coming in and out. A couple of years ago they had that.
"In the summer just gone, I don't believe there was so much change. They were able to keep the same players together and I think the manager that's come in is the right fit for those players.
"So I think it's things marrying together, and they're at that place now where they all have an understanding and know what each other is capable of.
"They have belief as well. They have the belief that they can do something so when you add those together, it's always going to be a good fit.
Quizzed on if they can reproduce a Leicester-style 'miracle', Blackett quipped: "I've heard that going around. You never say never in sports, do you? There's always that opportunity for a team to do something unexpected.
"I wouldn't write it off, but I do think there are other teams that may be stronger and may have a good run at the end. I hope they finish as high as possible and stay up there."
MLS on the come-up
His departure from Forest as a free agent in 2021 opened up the prospect of new opportunities for Blackett, which he took as he headed stateside to join FC Cincinnati in Major League Soccer.
It marked a reunion with treble-winning Manchester United defender Jaap Stam, who was his manager during his stint at Reading.
"It's different but the biggest (challenge) for me was the level of the players," Blackett said. "There are a lot of South American players in the MLS and they have great technical ability.
"I would say the level is a better level than the Championship in England – not the Premier League – in terms of the quality of player.
"There are more players that can do something and have a good level of ability to make passes, do a piece of skill or change the game."
MLS is becoming an ever-rising destination for some of the biggest names in world football, with none other than Lionel Messi at the forefront of the league's growth.
The Argentine superstar took the plunge and moved to the United States in July 2023 to join David Beckham's Inter Miami, where he plays alongside fellow Barcelona icons Luis Suarez, Sergio Busquets and Jordi Alba.
MLS is attempting to rival the massive salaries advertised in Saudi Arabia, which houses Messi's long-time rivals Cristiano Ronaldo and Karim Benzema, to name a couple.
And Blackett feels Messi's influence in MLS will go a long way towards increasing the quality levels across the division going forward.
"The eyes are now on the league because Messi's there. It creates that attention and there are more people that are drawn to the league to watch games and see how he's doing and how the games are played over there.
"From him being there, I think players in that Miami team and players he'll come (up) against will all want to emulate him. They'll all want to do what he's doing which raises the level.
"I think it's a great thing for the MLS and I think they are lucky to have him."