Manchester United's away day jinx continued as they were held to a 2-2 draw by a determined and disciplined West Brom side.
It was the least the Baggies deserved as van Gaal's side were left frustrated by another inconsistent performance.
West Brom made a lively start, United having to be alert at the back against the pace of Saido Berahino.
It took the away side a few minutes before they were able to put a string of passes together as they tried to settle into the game.
The United players were giving West Brom too much space though, and it was to prove costly as Sessegnon produced a first time finish from the edge of the area to give the home side the lead.
Wisdom was allowed to maraud down the right and picked out the Frenchman who smashed his effort into the top corner to leave de Gea with no chance.
United almost levelled moments later as Boaz Myhill was called into action to deny van Persie at the expense of a corner.
The Red Devils looked nervy at the back, Rojo getting in a mess and almost presenting Berahino with a chance inside his own penalty area.
Di Maria was causing problems for West Brom and the Argentine swivelled and shot in one movement as he got on the end of a long Blind pass, but the effort lacked the pace to beat Myhill.
United were starting to see much more of the ball and Di Maria stung Myhill's palms with a swerving strike from the edge of the area.
West Brom were still looking dangerous on the counter though, with Berahino stretching United's back line.
Van Persie almost made Lescott pay for dallying on the ball in his own area, but he chose to shoot himself instead of finding Mata, who was unmarked, and the chance went begging.
Louis van Gaal replaced Herrera with Fellaini at the start of the second half and it took just three minutes to pay dividends.
Di Maria crossed from the left and the big man showed strength to hold off Lescott and chest the ball down before smashing a shot unerringly past Myhill to equalise with his first ever goal for United.
The goal seemed to give United more purpose and Fellaini almost got in the end of a Januzaj cross as the substitute continued to cause problems for West Brom.
United were carving West Brom open, Januzaj and Rafael combining well down the right and Di Maria torturing the home defence down the left flank.
But just as it looked like United would go on to dominate the defence opened up like the Red Sea to allow Berahino a clear run on goal to steer an effort past de Gea and restore West Brom's advantage.
Van Persie struck an effort from the edge of the area off the base of the post with 16 minutes to go as United tried to find an equaliser and Januzaj smashed the rebound over when he should have done better.
United pressed for an equaliser, and just as time was running out up popped Daley Blind at the edge of the area to finish low past Myhill.
Fellaini hooked a shot at the West Brom keeper, but United couldn't find a way through and both sides had to settle for a point.
Written by Andrew
It was the least the Baggies deserved as van Gaal's side were left frustrated by another inconsistent performance.
West Brom made a lively start, United having to be alert at the back against the pace of Saido Berahino.
It took the away side a few minutes before they were able to put a string of passes together as they tried to settle into the game.
The United players were giving West Brom too much space though, and it was to prove costly as Sessegnon produced a first time finish from the edge of the area to give the home side the lead.
Wisdom was allowed to maraud down the right and picked out the Frenchman who smashed his effort into the top corner to leave de Gea with no chance.
United almost levelled moments later as Boaz Myhill was called into action to deny van Persie at the expense of a corner.
The Red Devils looked nervy at the back, Rojo getting in a mess and almost presenting Berahino with a chance inside his own penalty area.
Di Maria was causing problems for West Brom and the Argentine swivelled and shot in one movement as he got on the end of a long Blind pass, but the effort lacked the pace to beat Myhill.
United were starting to see much more of the ball and Di Maria stung Myhill's palms with a swerving strike from the edge of the area.
West Brom were still looking dangerous on the counter though, with Berahino stretching United's back line.
Van Persie almost made Lescott pay for dallying on the ball in his own area, but he chose to shoot himself instead of finding Mata, who was unmarked, and the chance went begging.
Louis van Gaal replaced Herrera with Fellaini at the start of the second half and it took just three minutes to pay dividends.
Di Maria crossed from the left and the big man showed strength to hold off Lescott and chest the ball down before smashing a shot unerringly past Myhill to equalise with his first ever goal for United.
The goal seemed to give United more purpose and Fellaini almost got in the end of a Januzaj cross as the substitute continued to cause problems for West Brom.
United were carving West Brom open, Januzaj and Rafael combining well down the right and Di Maria torturing the home defence down the left flank.
But just as it looked like United would go on to dominate the defence opened up like the Red Sea to allow Berahino a clear run on goal to steer an effort past de Gea and restore West Brom's advantage.
Van Persie struck an effort from the edge of the area off the base of the post with 16 minutes to go as United tried to find an equaliser and Januzaj smashed the rebound over when he should have done better.
United pressed for an equaliser, and just as time was running out up popped Daley Blind at the edge of the area to finish low past Myhill.
Fellaini hooked a shot at the West Brom keeper, but United couldn't find a way through and both sides had to settle for a point.
Written by Andrew