His signing, announced on Thursday, will provide United fans with a huge lift.
It will do so not because Herrera is necessarily a "world superstar" or a "big-name signing" but because he is precisely the type of player that United's squad needs most.
United's March 2012 clash with Athletic Bilbao in the Europa League was the first time fans of the Red Devils who do not watch Spanish football had a chance to see Herrera, who has penned a four-year contract.
His performance was highly impressive as Bilbao's midfield made light work of United's—Athletic's victory was a more than fair result.
Back in January of this year, I suggested United were correct to pursue Herrera, in spite of a number of caveats.
The first caveat was to do with his size. Herrera may be slight for a Premier League midfielder, but he is not afraid of the physical aspect of the game. His 3.1 tackles per game are indicative of his style.
The second caveat was his form. In the first half of last season, Herrera was often played out of position, and it may even be that the deadline-day drama of a potential move to United had some bearing on his performances. Since that article was written, Herrera has found his best form again.
His overall statistical contribution to Bilbao's season has been excellent. Five goals and five assists in La Liga dramatically exceed any of United's midfielders' league contributions (or indeed overall contributions), and his 1.6 key passes per game are a 60 percent improvement on Michael Carrick's, for example.
The statistics also show he is fond of a dribble, and someone who can run with the ball is something United's midfield sorely lacks, especially now that Ryan Giggs has retired. Anderson is the only other player on United's books with similar proclivities, and given his paucity of all-round contribution, he hardly seems the answer.
Herrera's average of 1.2 dribbles per game hopefully means United fans will have plenty to get them out of their seats at Old Trafford.
The third caveat was the price, which is certainly high, but given United's lack of Champions League football next season, paying a premium for quality players seems inevitable.
It is vital that United strengthen to a level which allows a swift return to the elite competition in Europe, whatever the cost.
The costs of not doing so will be far greater.
Whilst the upgrade in manager may have been the single most important change United could make, the addition of quality in the centre of midfield was a close second place.
And what quality it is. Herrera is comfortable with or without the ball. He is fond of a shot. For some context, Michael Carrick took an average of 0.6 shots per game last season and Herrera an average of 2.1.
Much of United's midfield play became entirely predictable last season. Partly this was the "David Moyes Effect." The team's tactical outlook was dominated by wing-play, and there was not a great deal of creativity on show from central midfield.
However, Moyes is not entirely to blame for this. The personnel available to him were distinctly lacking in "spark."
Fond of both shooting, dribbling and finding a key pass, Herrera is a player who can provide plenty of spark.
As well as being a signing of any kind—a much-needed fillip for fans who have seen several of United's rumoured targets rule themselves out of consideration—he is also the right kind of signing.
In January, I described his signing as a gamble. Whilst all signings, of course, carry an element of risk, this one feels much less of a gamble now than it did then.
Partly this is because of Herrera's improvement in form, partly it is because United's need is greater and partly it is because United now have a manager whose capacity to get the very best out of his players is not in question.
A truly high-quality central midfielder has signed for Manchester United. Will wonders never cease?
All statistics per Whoscored.com