Manchester United started the defence of their Premier League title with a 2-1 victory at West Bromwich Albion but Sir Alex Ferguson was left to lament a "torrid few days" after Rio Ferdinand and Nemanja Vidic picked up injuries to join Rafael Da Silva on the sidelines.

The United manager is hopeful that Vidic, who has a calf problem, will be out for only a fortnight but Ferdinand will be sidelined for six weeks with a hamstring injury. Ferdinand will miss United's home Premier League matches against Tottenham Hotspur and Arsenal as well as England's Euro 2012 qualifiers against Bulgaria and Wales next month. He would also appear to be struggling for United's trip to Chelsea on 18 September. Da Silva, meanwhile, is due to undergo an operation after he dislocated his shoulder in training on Friday. The full-back will be out for 10 weeks.

Although Ferguson described the availability of Phil Jones, Jonny Evans and Chris Smalling as a "godsend", he left The Hawthorns with another potential selection problem on his hands after David De Gea continued his difficult start in English football by giving away a goal for the second weekend running.

The 20-year-old Spaniard, who was signed for £18m from Atlético Madrid in the summer, allowed Shane Long's tame shot to slip under his body, handing Albion an equaliser after Wayne Rooney had put United ahead. An own-goal by Steven Reid nine minutes from time ensured that United got off to a winning start but it was far from a comfortable afternoon for Ferguson, in particular because of the injuries.

"We've had a torrid few days," he said, "but at least Patrice [Evra] will be back next week so we've got options." United's next game, against Spurs, is a week today.

Ferguson will also have to decide whether he should bring in Anders Lindegaard to replace De Gea in goal after his latest blunder. "Young David should have done better with the goal – just a bit of concentration there – but welcome to English football, because he took a battering in the second half. He should've got more protection from the referee but he wasn't [given it]. He had to withstand that, so it's a good experience for him. He is young. He will learn. He will come through.

"I couldn't believe he never got a free- kick. The aerial assault on him was ridiculous. He was targeted a bit. Not necessarily physically but there were a lot of challenges that should have been free-kicks but the referee decided to play on.

"I think my recollection of goalkeepers coming from Europe is that it's a learning process, it's a different game. Peter Schmeichel was the same when he came – his first away game was Wimbledon and they gave him a torrid time and then the following Saturday against Leeds United he lost a really bad goal. But Peter went on to be the greatest goalkeeper of all time possibly. The boy [De Gea] is only 20 years of age and it's a learning process for him too at the moment and he'll see it through. You just give him a pat on the head and say welcome to England."

Meanwhile André Villas-Boas admitted some frustration at emerging with only a point from his first competitive game in charge of Chelsea, though the new manager qualified that disappointment with an acknowledgment of the unique challenges faced by visitors to Stoke City.

Chelsea endured an awkward afternoon in the Potteries, having to contain their hosts through the first half before imposing themselves more impressively after the break. "A point is not ideal but not the end of the world in my opinion," said Villas-Boas. "For our title challenge it is not the greatest start to the Premier League, of course, but this really is a difficult ground to play on. Look at their record from last season, when they won 10 matches. That showed the quality."

The Portuguese, who had selected Fernando Torres in preference to Didier Drogba for the fixture, was left unimpressed by "the amount of pushing and grabbing in the box" his players endured at the hands of Stoke, and suggested he would bring the issue up when he is visited by a referee, sent by the Professional Game Match Officials Board, later this week.

"It was out of this world," he added. "There's a limit to the pushing and grabbing that makes it impossible. Referees have to pay attention to these kind of details.

"I may raise this on Wednesday but I know it is difficult. Referees have to keep their eye on the ball but also be aware of certain other situations around. In this case maybe the referee is in need of some help, perhaps in terms of fourth official awareness, his assistants or a greater focus on the situation."