As Wearside waits anxiously to see if Brian Brobbey's withdrawal from the Netherlands squad is injury or merely fatigue related, a key issue Sunderland have faced this season has again been brought into focus.

Coming into the campaign, much of the debate about Sunderland's prospects centred around what impact European football would have on their squad in terms of fitness and fatigue. Though at times Régis Le Bris has hinted that he feels it has perhaps distracted or complicated things in terms of preparation for the Premier League game on the Sunday, the Europa League at this stage can't really be blamed. Most of Sunderland's squad have played European football in the past, and Le Bris has rotated his squad heavily enough to ensure no one has faced a particularly punishing workload. What has quite clearly had a very negative impact on Sunderland's campaign so far is international football.

Yes, it's the same for all Premier League teams, but Sunderland had one of the largest cohorts at the expanded World Cup in the summer and again in the most recent set of fixtures. The toll both have taken has been obvious.

The factors behind Sunderland's disappointing start to the campaign are myriad, and if you had to pick the primary one you would surely have to go for the regular disruption in defensive partnerships and the big individual errors that have followed. Speaking ahead of the crucial 1-0 win over Chelsea that has sparked hopes of a revival in the weeks and months to come, Le Bris wondered if maybe at the start of the club's second season the sense of an underdog spirit had been eroded a little. The surge in intensity and individual performances that followed against big-six opposition would suggest he was right. Le Bris also pointed to one of football's recurring truths, that playing not so well but winning can build confidence that sees levels then rise. Playing well but not getting over the line, in Sunderland's case because of poor finishing and those individual errors, can knock confidence and lead to a decline in performance.

“It’s complex," Le Bris said.

"It’s hard to find just a single reason [for the poor start]. The second season is also a little bit more difficult, because you don’t start from scratch. Now you have to confirm, rather than showing  everything. Maybe the underdog spirit is a bit different. But I still think they have the ambition.

“The World Cup was tough with 12 players involved so pre-season was a bit different. After that it’s a question of momentum. We started with a good level but we were not rewarded. Maybe last season the level wasn’t so high but we were rewarded. So the momentum is a bit different, the energy. So it’s always complex."

Le Bris is too diplomatic to point to the key positions Sunderland weren't able to recruit in over the summer as an additional factor, which it quite clearly is. But the point about international football is a key one.

Granit Xhaka played 51 games for club and country from his arrival at Sunderland to the end of the World Cup, and has barely missed a Premier League minute since. Yes, he missed the last set of international fixtures but is it any wonder that at 34 he has looked fatigued and then suffered a muscle injury? Omar Alderete battled knee issues during the World Cup which meant he had no pre-season to speak of on Wearside, and has looked badly out of form since as he tries to play catch-up with his match fitness. Dan Ballard and Brian Brobbey both have had a heavy workload over the last year and suffered muscle injuries during the last international break. That extended break was brought in primarily for player welfare, yet the feeling within the game was that it had the opposite impact and you suspect Sunderland would strongly agree. Not only did they suffer those injuries, but a number of players saw their form dip when they returned. Trai Hume played four games in 11 days during that break, Kevin Danso three: neither looked the same as they did in the weeks previous.

Sunderland are still building the depth of their squad in a challenging SCR environment, and they struggle at the moment to manage the drop off when key players are unavailable. We saw that clearly when Brobbey was absent most recently with a hamstring issue, when the team lost their focal point and ability to get up the pitch in games where they are struggling.

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International football and the challenges it brings are of course part of the journey as a Premier League side, and something that Sunderland can't use as an excuse for their league form. It's nevertheless fair to point out that the unique nature of the international schedule over the last six months has brought its challenges, and most definitely offers at least one small reason as to why they haven't been able to enjoy the continuity from the end of last season that underpinned their approach to the summer transfer market.

Though Jules Ahoka's performance against Chelsea means Xhaka's injury might not be quite as big a blow as it would have been a month ago, it would still badly damage Sunderland in losing their most progressive passes and in limiting Le Bris's options to rotate across another busy schedule. Sunderland's performances without Brobbey this season speak for themselves. With twelve further players in international action over the next week, it will be an anxious time on Wearside. The last break showed how quickly circumstances out of your control can take away any sense of momentum.