Van Gaal is still waiting for his first Barclays Premier League win as Red Devils boss, having lost the opener against Swansea and then been held to draws by Sunderland and Burnley
Their stuttering start to the season, which also includes a 4-0 Capital One Cup defeat to MK Dons, has prompted criticism of Van Gaal's preference to play with three at the back, and Souness is not sure the formation will work for United given the players at the Dutchman's disposal.
"If Van Gaal is determined to persist with a back three, this is going to be a long and painful transition for United," the former Liverpool, Rangers, Blackburn and Southampton boss wrote in his Sunday Times column
"The team may take until November to settle down
You ain't going to win the league if you take that long and you might not make the Champions League places either
"United have already dropped seven points from a possible nine
If you continue with three at the back and the results are not improving players will not be slow in turning round and pointing their fingers at the coach, saying, 'It's not that I am not playing well, it's the system'."
Souness went on to say that he does not think the system, which Van Gaal employed so successfully for Holland during the World Cup in Brazil, will bring out the best in British record signing Angel di Maria, a £59.7million recruit from Real Madrid last month.
The Scot added: "Angel di Maria is too much of a winger to play as a wing-back, so he could play one position inside the widest man in a 3-5-2.
"If you play with a back four you can play him wide, as Argentina did when he made three goals and scored the other in their 4-2 win over Germany in midweek
I don't read much into international friendlies but that performance showed his talent."
United have the chance to record their first Premier League victory of the season next Sunday when they face QPR at Old Trafford.
Source : PA
Source: PA