Ole Gunnar Solskjaer has been here before; the Manchester United manager seems to face the "biggest week" of his time in charge of the club regularly. But this one really does feel like it, with season-defining games against RB Leipzig and Manchester City within the space of five days for a team that has become, arguably, the most unpredictable in Europe. This week is a fork in the road for Solskjaer's United and they really could go either way, towards success or failure.

Nobody knows which United will turn up, least of all their manager. It could be the side that was overrun for 45 minutes at West Ham on Saturday, or the team -- with the aid of half-time substitutes Bruno Fernandes and Marcus Rashford -- that demolished David Moyes' side in the second half with a breathtaking display of counter-attacking football and world-class finishing to win 3-1 at the London Stadium. Or the one that was 2-0 down at half-time at Southampton a week earlier before winning 3-2 at St Mary's. Or the one that beat Leipzig 5-0 at Old Trafford in October, or perhaps the United side that lost 2-1 at Istanbul Basaksehir a week later.

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Those wildly contrasting results and performances sum up Solskjaer's time as manager at Old Trafford. He will mark the second anniversary of his appointment, initially as caretaker following Jose Mourinho's sacking, on Dec. 19, but his trajectory has mirrored that of a roller-coaster with ups, downs, lurches and peaks of excitement. What happens this week will be crucial in telling us what progress has been made and where, exactly, Solskjaer and United are headed.

With two wins, United will book their place in the Champions League round of 16 and become a live contender in the race for the Premier League title. A draw against Leipzig will also be enough to qualify from Group H, but United would then almost certainly surrender top spot to Paris Saint-Germain and risk being drawn to play the likes of Bayern Munich, Barcelona or Juventus.

It is the damage of defeat in either game, though, that Solskjaer and United should be worried about.

If they lose in Germany on Tuesday, United will crash into the Europa League after needing just a point from their final two group games to progress in the Champions League. If that happens, the defeat in Istanbul and Solskjaer's failure to substitute Fred before the midfielder's inevitable second yellow card in last week's 3-1 defeat at home to PSG will be cited as evidence of his shortcomings as an elite manager. Equally, a defeat against City at Old Trafford will not only shatter the momentum United have been building in the Premier League, but would also highlight their dismal record against the "big six" so far this season, which has seen them lose to Tottenham Hotspur and Arsenal and draw with Chelsea -- with all of those games being played at home.

It really does feel like a case of "here we go again" with Solskjaer and United, because there have been so many examples of crucial weeks in the past two years. That said, Solskjaer usually, somehow, finds a way to keep the storm clouds at bay by overseeing a win when he needs it most.

So is he the man to take United back to the top, or a stopgap who has only survived this long because of his status as playing legend at the club during Sir Alex Ferguson's glorious reign as manager? Within the club, the response would be the former. Senior figures at United believe that Solskjaer has put the team back on track by restoring the club's vision of promoting youth and embracing a more collegiate approach to player recruitment. Results have been unpredictable, but sources have told ESPN that United are confident Solskjaer has brought about a positive change and that it merely requires time and patience for greater consistency to develop. Once that happens, it is hoped results and success will follow.

Some at United will point to the example of Jurgen Klopp's first two years at Liverpool, which was a similar tale of highs, lows and inconsistency. Just like United this week, Klopp's Liverpool, who were fourth in the Premier League at the time, went into their final Champions League group game in December 2017 needing to avoid defeat to progress. They won that game, qualified for the knockout phase and signed Virgil van Dijk from Southampton on Jan. 1, 2018. Liverpool have not looked back since.

If United were to find a commanding midfielder in January -- a player capable of dictating the tempo of the game and knitting Solskjaer's talented, but unpredictable, squad together -- then perhaps they could follow the Liverpool path. But that type of player rarely comes along, which puts the onus is on Solskjaer to square the circle and prove, once and for all, that he has the skill set to compete with Klopp, Mourinho and Pep Guardiola.

This is the tricky part, however. Within the game, it is difficult -- if not impossible -- to find a player, scout or agent who will say that Solskjaer is an elite manager. Privately, many will question his tactical acumen and ability to inspire. Some will dismiss him as no more than a coach elevated way beyond his natural level simply because of his connection to the club as a player.

"Players want to sign for Klopp or Guardiola, but you will struggle to find any who will say they want to play for Solskjaer," one agent told ESPN. "He doesn't look like the boss, and I think that explains why United's performances have been all over the place -- the players know he doesn't have the same status or control as the very top managers."

Yet despite all of the doubts, Solskjaer has put United back in the Champions League and they are showing signs of being a title contender again. Perhaps Solskjaer is on the brink of taking himself and United to the next level, but maybe the doubters are right and he can only take the team so far. By the end of this week, we will all have a much clearer picture of what the future looks like for Solskjaer and United.