The £12m Sunderland paid Wolves for Steven Fletcher raised eyebrows last summer but no one could argue now the 25-year-old former Hibernian strikerhas not given value for money. The two first-half goals here brought his total to 10, all in the Premier League, and the second was a finish of such class it may cause many to make a fundamental reassessment of his abilities.

Not Martin O'Neill, obviously. The manager has long since been convinced Fletcher has been, and to some extent remains, underrated in certain quarters. "The transfer seemed to be a bit of a saga at the time but it was well worth it," he saidafter watching his side rise to 11th after winning five of their past eight matches.

"We relied on him at the beginning of the season; he was the only player scoring for us. Since then we've shared a few goals around but he's a really top-class centre-forward, not just with his goals but in the way he brings others in to play. For one not so tall he's strong: what Sir Bobby Robson called 'a proper centre-forward'."

Even that may be underselling him, a little. The free-kick that Craig Gardner pumped high towards the Wigan penalty area shortly before half-time was hit more in hope than expectation but Fletcher, having glanced the ball on, turned and stroked Adam Johnson's lay-off first time in to the top corner of Ali al-Habsi's goal with the sort of unerring, instinctive certainty that one associates with the likes of Robin van Persie or Luis Suárez.

The goal came at the end of a frantic and hugely entertaining first half during which David Vaughan's own goal gave Wigan an ideal start before Gardner equalised from a penalty given when Sebastian Larsson's free-kick struck James McCarthy's upraised arm as he jumped to block. Fletcher then put Sunderland ahead with a stylishly emphatic close-range volley after Habsi had blocked his initial header, and although Angelo Henríquez pulled back a goal 11 minutes from time, the visitors, roared on by almost 5,000 travelling supporters, clung on.

While O'Neill happily and justifiably paid top dollar for Fletcher, the £3.5m or so he has just paid Bursaspor for the 22-year-old French midfielder Alfred N'Diaye could prove equally well spent. Making his full debut, N'Diaye missed an early headed chance and misplaced a pass or two as he tired, but otherwise he was outstanding, breaking up countless Wigan attacks with well-timed tackles and interceptions, running from box to box with impressive energy, and passing intelligently and creatively. It was his cross from the left that created Fletcher's first goal, and as O'Neill remarked, his strength and size brought an added dimension to Sunderland's football.

"He's really strong, he's got a bit of energy and vitality and I think when he gets to grips with the league he'll be a decent asset," O'Neill said. "We've lacked a bit of physical presence, certainly for the 13 months since I've been here, and he maybe gives the smaller players a chance to play.

"There's a bit of competition for places developing now, which is something we haven't had here for quite some considerable time. There's definitely been a response from the other players."

Given their dominance of the second half Wigan's manager Roberto Martínez was probably justified in maintaining his side deserved at least a point, but their home record this season, two wins in 12 games, is threatening to end their eight -year stay in the Premier League.

Martínez, who dismissed reports linking McCarthy to Arsenal, said the £4m profit made by the club last year meant he did not need to sell and is in a position to bring in a replacement for centre-half Ivan Ramis, out for the season with a cruciate ligament injury. Both are necessary.

Man of the match Steven Fletcher (Sunderland)