After 28 games of Manchester United’s Premier League campaign, Louis van Gaal may have hoped last summer’s £150m-plus splurge on Radamel Falcao, Ángel Di María, Marcos Rojo, Ander Herrera, Luke Shaw and Daley Blind would have reaped a richer dividend.

To stand 10 points behind the leaders, Chelsea, and have Champions League qualification dangling precariously, with Liverpool, Tottenham Hotspur and Southampton all no more than four points behind, was not in the masterplan when Van Gaal sanctioned the spending. He would, though, have had FA Cup ambitions in mind and a semi-final place will be secured if United beat Arsenal on Monday night.

Since the six can be broadly divided into galácticos (Di María and Falcao), solid performers (Blind and Rojo), and future prospects (Shaw and Herrera), the signings appeared a shrewd blend.

They would be a cocktail of superstar performers, reliability and youth injected into a United squad finally receiving the major surgery that had been required for the previous two seasons, at least. All – apart from Herrera – were senior internationals, so the demand that Van Gaal deliver a Champions League berth appeared a shoo-in. Yet Blind aside, all have struggled for a variety of reasons: form, injury, the manager’s erratic selection policy and adjustment to life at a club of United’s profile. In the statistical roll call of all Premier League signings made this season, the respective worth of each of the sextet can be found.

In Falcao’s 17 appearances he has scored four times at 251.25 minutes per strike. This places the Colombian seventh in a list headed by Chelsea’s Diego Costa – 21 games, 17 goals at 104.76 each – with Diafra Sakho (West Ham), Alexis Sánchez (Arsenal), Loïc Rémy (Chelsea), Leonardo Ulloa (Leicester City) and Mame Biram Diouf (Stoke City) all above him. The 29-year-old, who cost a total of £16m for his season-long loan, is a shadow of the fearsome predator who crashed a hat-trick past Chelsea for Atlético Madrid in the 2012 Uefa Super Cup final. In 2013 he joined Monaco and the serious knee injury he suffered in January 2014 while playing in a French Cup match appears to have left him a vital fraction slower.

In the successful pass chart, which is topped by Chelsea’s Cesc Fèbregas (1,701 in 2051 minutes from 24 games), Di María’s 581 in 1,481 from 20 appearances rank him 17th. Yet as the Argentinian’s eight assists are second only to Fàbregas’s mark of 15, this illustrates the uneven campaign of a 27-year-old who has shown flashes of why he cost a British record £59.7m and was a prime factor in Real Madrid’s La Décima European Cup triumph last May. The black mark against Di María is that he can run up too many blind alleys. His stock is so low that Van Gaal replaced him at half-time and after 59 minutes in United’s past two matches.

Herrera’s 693 successful passes rank him 11th. But considering the limited game time he has had – only 975 minutes from 16 appearances – this is a respectable count from the Spaniard, who has suffered from Van Gaal’s odd decision to prefer Wayne Rooney in midfield. Given a chance to play regularly – the 25-year-old has started United’s past four matches – Herrera who cost £29m from Athletic Bilbao, has performed with sufficient distinction to be voted the club’s February player of the month by fans.

While Herrera’s progress has also been hampered by four separate injuries, Shaw (a £30m buy from Southampton) has endured the first injury-disrupted season of his nascent career. After knuckling down to Van Gaal’s demand in the summer that he should be fitter, a hamstring problem prevented the 19-year-old starting the season and this has been followed by a damaged knee, two differing foot injuries and two more hamstring complaints. All of this seems to have taken the edge off Shaw’s pace and the left-back’s defending, though the injury lay-offs are a mitigating factor in his ranking 33rd in successful tackles. The 15 made have been from 916 minutes of Premier League action in 13 appearances.

Rojo’s numbers are better but still underwhelming, though injury has twice ruled him out for around a month. The 24-year-old defender, who played all 120 minutes of Argentina’s losing World Cup final against Germany last summer, ranks 12th in successful tackles, with 30 from 1,300 minutes played in 17 games. Martin Kelly of Crystal Palace with 65 is the best and other defenders ahead of Rojo include Phil Bardsley (Stoke), Alberto Moreno (Liverpool) and Joleon Lescott (West Bromwich).

Blind, though, can be content because he has been consistent in the (predominantly) holding midfield role he has operated in despite a knee injury suffered in mid-November that ruled him out for two months. The Dutchman’s numbers illustrate his metronomic abilities, ranking fourth in successful passes, with 947 from 1,389 minutes in 16 Premier League matches.

Yet given the club’s eye-watering investment far more was expected from this group. Now, 10 matches remain in which to finish the season in stronger fashion, and propel United to a top-four finish.