Robin van Persie's flying start to his Manchester United career continues. On a night when the questions kept on coming for Sir Alex Ferguson's side, the 29-year-old took his tally to seven goals in eight appearances, though the two he scored here will not deflect further inquiries into United's sluggish midfield and defence.

Both goals were created by Wayne Rooney, who may finally have found the productive strike partner he has lacked in his 10-year career with United, Everton and England.

"I am on the way to settling in well," said Van Persie. "It is not only about goals but I want to make more assists. I am on a good run but I would like to do better."

When Ferguson picked his team he hoped the focus would be on the two players he selected together for the first time and not on his rearguard. After injury, match fitness and form had prevented the pair playing in tandem United supporters would finally see Rooney and Van Persie in the same starting XI.

In all Ferguson made six changes with Shinji Kagawa the headline absentee as the Scot retained the same back four that had been exposed in Saturday's 3-2 defeat by Tottenham Hotspur.

With no Antonio Valencia, Ryan Giggs and Nani, who was on the bench, this was the narrowest set-up sent out by United in recent memory. While they may have walked off 1-1 at the break United had stuttered through the first half – with their lack of width allowing Cluj's containment job broadly to be confined to the parameters of the 18-yard box.

Early on Rooney, who delivered United's corners in the absence of a regular specialist, found his accuracy wanting when one long pass intended for Javier Hernández's feet went straight to a maroon shirt.

Rio Ferdinand, who bore much of the criticism for defeat by Spurs, made the first mistake. A poor clearance gave away a corner though, when Rafael Basto's cross to Ionut Rada led to nothing more dangerous than a second one, it did no damage.

Cluj's previous home match here ended in a 5-1 rout of Gloria Bistrita. For this one the locals had their camera phones trained on all parts of a ground in which Chelsea had drawn 0-0 four years ago at a similar stage of the competition – and where United were about to be shocked.

Fourteen minutes had passed when Romania's champions took the lead. As on Saturday this was too easy. Bastos, the Brazilian striker, dropped off before aiming a sweeping diagonal pass to Modou Sougou. Patrice Evra should have done better than allow the Senegal winger to cross and Pantelis Kapetanos went unchallenged by Jonny Evans before the Cluj No9 finished past David de Gea. The stadium announcer deliriously shouted "gooaaaaaaaaaaaaaaalll!" to greet it with the home crowd going mad.

Rocked, United moved forwards from the restart and won a corner. But when Rooney's cross came back to him he could deliver only a centre that Mario Felgueiras punched to safety.

Later the home keeper must have felt disappointment at United's equaliser. Cluj had held their lead for 15 minutes when Hernández won a free-kick on the left. Rooney stepped up to find Van Persie and his attempted header came off a shoulder sending the ball looping over Felgueiras.

At the break Ferguson strode off hardly enamoured at what he had witnessed and with the look of a man about to turn his notorious hairdryer up a notch or two.

Speaking at halftime he said: "We are doing most things correct in terms of passing, but losing that goal the way we did is a shocker. An absolute shocker. The way Cluj play everyone is behind the ball, that is what they are built on. The counter attack is what they love to do, they will just sit in their and just hope to hang on."

When his side re-emerged the manager had resisted tinkering with his 4-3-2-1 by, say, introducing Nani and giving Ioan Andone's side a different problem. Instead they could thank Felgueiras again when they quickly took the lead after another contribution from the Rooney-Van Persie axis. Rooney flicked in an elementary cross from the right which the Portuguese keeper should have dealt with comfortably. But he charged out and Van Persie steered the ball past him with ease.

There was a scare at the end when De Gea – who had a fine evening – made a sharp save from Bastos. "He's acclimatising to English football, which is sometimes difficult, but he showed tonight how good he is," Ferguson said.

The Scot, though, will not relish watching the tape of this display.