This summer was supposed to mark the start of a new era at Manchester United. Instead, so far, it's been the same old story.

Rather than new owners sweeping into Old Trafford to inject new life into a sleeping giant of a football club, supporters have seen their rivals take the first steps in the transfer window. Of the Premier League's traditional top six -- which has expanded to seven following Newcastle United's return to the Champions League -- all but one have signed at least one new player in readiness for next season, or are at least very close to doing so. No prizes for guessing the odd one out.

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United manager Erik ten Hag enjoyed a relatively successful first season in charge -- winning the Carabao Cup, reaching the FA Cup final and finishing third in the league -- but he will know better than anyone that if you stand still in the Premier League, you end up moving backwards. Just ask Jose Mourinho.

In 2017-18, Mourinho's second season in charge, United finished second behind Manchester City and reached the FA Cup final, where they were beaten by Chelsea. There was cautious optimism that, with a productive transfer window, they could close the gap on Pep Guardiola's team and become serious title contenders for the first time since their last triumph in 2013. But by the time Mourinho turned up in Los Angeles for the start of United's preseason tour in July 2018, he was already convinced he wouldn't get the financial backing he believed he needed.

Stoney-faced from the minute he arrived in California, he was asked in his first news conference at UCLA whether he was optimistic about United's chances of challenging City. He refused to answer. After another news conference, he gestured to the gathered English journalists that he wanted to speak to them away from the cameras. Huddled in a corner, he revealed was keen to get rid of Anthony Martial, only for executive vice-chairman Ed Woodward to say a few days later that the French striker would definitely stay.

Mourinho's mood was so bad throughout the tour of the United States that when talk show host James Corden arrived at the training ground to film a segment for "The Late Show," the United manager initially refused to take part, only relenting at the last minute. The final insult for Mourinho was Woodward and the recruitment team vetoing a move for Jerome Boateng because of the Bayern Munich centre-back's injury record, and by the end of the tour Mourinho and Woodward were barely on speaking terms.

The cautious optimism of early summer had long gone by the time United began the new season with just five wins from their first 13 games. Mourinho was gone by Christmas.

Ten Hag might not have Mourinho's fiery attitude in front of the media, but when it comes to improving the squad, he can be equally demanding. The Dutchman views it as a manager's job to challenge the board and, as he puts it, "always want more."

He's sympathetic to the club's financial position, with the transfer budget limited by Financial Fair Play (FFP) restrictions. But he would still like at least a striker, a midfielder and a goalkeeper before the season starts. United have had three bids turned down by Chelsea for Mason Mount, although their latest offer of £55 million ($69.9m) remains on the table. There's also interest in Harry Kane, Rasmus Hojlund, Moises Caicedo and Andre Onana among others but, so far, valuations set by opposing clubs have proved problematic.

Concerns over FFP mean United can only realistically spend between £100m and £150m on new players, and although that figure would increase with any funds raised through departures, the financial position can be summed up by their interest in Jude Bellingham and Declan Rice. Ten Hag likes both players but United were nowhere near when Bellingham joined Real Madrid for Borussia Dortmund for an initial £88.5m, simply because they couldn't afford it. It's a similar story with Rice, a player tracked since he was a teenager, because of West Ham United's demand to receive £100m up front. Arsenal are leading the race for his signature ahead of Manchester City, with United in a distant third.

United insist there's money to spend -- the latest financial results released on Tuesday showed £73.7m of cash or cash equivalents plus a projection of record revenues for the year -- but they will have to be careful about how it's used.

It's impossible to judge a transfer window until it's closed, but the uncertainty around the club is doing Ten Hag no favours at all. When will there be clarity on the ownership situation, with the Glazer family evaluating takeover and minority investment offers? What's happening with Mason Greenwood, who is on United's list of retained players but the club are yet to make a decision on his future? Will David de Gea sign a new contract? What will the squad look like next season? These are questions which need to be answered, ideally before the preseason tour of the U.S., which kicks off in New York City on July 20.

As Mourinho found out, optimism generated by a positive season can be quickly washed away by an idle summer. Long gone from Old Trafford, he still views the 2018 window as a missed opportunity to build a team capable of matching City's.

Ten Hag is the latest United manager attempting to rein in Guardiola and his team but even early in the summer, there's a danger that history is repeating.