Phil Smith's verdict: Why Lee Johnson believes this narrow win underlined a key improvement to his Sunderland side

It was a discussion becoming increasingly fraught, hope that Jermain Defoe would make a stunning and uplifting return giving way to the anxiety that he could end up pulling on a rival shirt.

Lee Johnson was given the opportunity to clear that up once and for all after the game, and could not have delivered a more emphatic response.

Yes, there are some minor reservations in that both he and the club are eager to ensure that everyone is absolutely satisfied with a deal, both with regards to the terms and the squad role moving forward.

But he wants and will pursue a deal for a player who he has a 'lot of respect for'.

"Don't mistake us being thorough for a lack of interest," was the most telling quote.

That Sunderland need a striker is obvious.

Ross Stewart was again superb here, with little sight of goal but another performance of impressive industry and a smart assist for what proved to be the winning goal.

Unprompted, Danny Cowley said afterwards that his defending from the front is what makes him the best forward in the division.

But depth is needed even if Nathan Broadhead looks on track to return from his hamstring injury, and if it is a player who can dovetail neatly with Stewart then all the better.

Whether it be Defoe or somebody else, a strong striking addition would be a significant boos for the automatic promotion hopes that remain very much alive after this hard-fought but vitally important win.

There was significant evidence within that win, however, to lend credence to the belief behind the scenes at Sunderland that perhaps their biggest January signing (both literally and metaphorically) may already be through the door.

The numbers behind Danny Batth's debut performance were impressive enough: 11 out of 12 headers won, five clearances, three interceptions.

Even more significant was the calm brought to the defence despite limited gametime and only a few days on the training ground to work with new team-mates.

Early days, for sure, but in a part of the pitch where Sunderland have long gifted the physical advantage to their opponent it looks as if they have finally been able to make a significant upgrade.

Batth's aerial dominance seemed to calm those around him, Callum Doyle having one of his best games in a Sunderland shirt.

"We need to win all types of games and it's something that I recognised early in the season and that I don't think we addressed early enough, and the signing of Danny certainly does that, giving us that dominant first-ball winner," Johnson said afterwards.

"I thought Danny was brilliant.

"He's got that physicality and takes the emphasis off Flanno in that regard.

"In possession he was good and played a couple of good long balls.

"There's not much to criticise his performance, and considering he hasn't been an absolute regular at Stoke, it shows his professionalism to churn out that 90 minutes."

Johnson's point about the first-ball winner was the key one. Though Sunderland have good defenders with some outstanding attributes in some cases (particularly Doyle's distribution), there has been a vulnerability to the long ball.

If Batth can go some way to dealing with that, then this Sunderland team will be a stronger prospect in the closing stages of the campaign.

They will need it, too.

This was a poor game for large stretches and that owed much to a pitch that is in desperately poor shape, not befitting a Stadium of this calibre and in truth, a source of some embarrassment for a club whose stated aim is to return to the top tiers of the game.

Most importantly, it is now actively hampering the club's playing philosophy.

Portsmouth dominated the early stages of the game, Sunderland looking short of confidence and energy. Much of that stemmed from a pitch that made playing out from the back and building quickly through the lines borderline impossible.

Cowley's main frustration with what proved to be the winner was that his side had not heeded that lesson, themselves caught out by trying to play out from a goal kick.

It should also be said that it was to Leon Dajaku and Elliot Embleton's credit that in the absence of Alex Pritchard, they stepped up in leading the press behind Stewart.

The pitch is unlikely to improve significantly until spring nears, and so the Black Cats will be forced to reluctantly tweak their approach.

It may have to be a little bit more direct, and they can expect to face more of the same in return: Batth's arrival is timely.

After two deeply disappointing results this was always going to be an afternoon when the result was significantly more important than the performance.

That Sunderland are still searching for the attacking fluency they had over the festive period is clear, and getting Patrick Roberts up to speed will be an important part of that.

They were fortunate that Portsmouth seemed to run almost entirely out of steam in the second half, barely forcing a save from Thorben Hoffmann after that dominant start, but they also found a decent balance between maintaining an attacking threat and giving their opponent little space in which to play.

A long injury list and a poor pitch will continue to present challenges over the next month, but after a testing period Johnson and his side have a platform from which to build.

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