Chelsea are gearing up to take on Wolfsburg in the first leg of their Champions League quarter-final. The Blues are in electric form, but it could well be an old foe who makes the difference this Wednesday.Given their current form, you’d be forgiven for thinking Emma Hayes was brimming with confidence heading into Chelsea’s Champions League quarter-final match against Wolfsburg on Wednesday.The Blues’ boss has led the club to five victories in their last six, scoring 16 times and conceding just once in the process — a consolation goal to Atlético Madrid after Chelsea had all but secured their passage through to the next round.The form of Fran Kirby in particular has been singled out for praise. Having recovered from various injuries over the years, Kirby is now in the best form of her career, as she demonstrated recently in the Continental Cup Final, netting a brace en route to lifting the trophy.Sam Kerr is another in red hot form. The Australian international made a relatively slow start to life in England but has since exploded, lighting up the WSL and striking fear into defenders up and down the country. Such has been the level of Kerr’s performances, Chelsea’s 2020 Player of the Year, Bethany England, has struggled to keep pace.And yet, despite the avalanche of positivity surrounding Chelsea at the moment, Hayes was far more studious in her response when asked about the European challenge that lay ahead.She is right to be cautious. Wolfsburg were last year’s runners up in the Champions League, and hold a huge psychological advantage over the West Londoners, having eliminated them from the competition in three consecutive years between 2016-2018 — the last of those by a crushing 5-1 aggregate scoreline."I'm extremely curious to see how far we've progressed in the last three years,” Hayes told Sky Sports earlier this week. "The way we're playing, I'm sure we've got qualities that will hurt Wolfsburg."There is little doubt in Hayes’ second remark; the aforementioned firepower of Kirby and Kerr is enough to blow any team out of the water on their day. But it may well be another Chelsea forward who ends up playing a defining role against the German giants.Step forward Pernille Harder. Similar to her strike partners, Harder has been in sensational form of late — something that was duly recognised by fans when she was voted the GiveMeSport Women FA WSL Player of the Month for February.

Harder arrived in England last summer after moving from Wolfsburg for a world-record fee of €300,000 (£259,000). Having spent three seasons with Die Wölfinnen — amassing a staggering 105 goals in 114 games — Harder knows better than most just how formidable her ex-club can be.

That knowhow could prove invaluable to Hayes and Chelsea, who are aiming to become the first English side to win the Champions League since Alex Scott helped secure the trophy for Arsenal back in 2007.

Wolfsburg, on the other hand, are seeing their domestic dominance questioned for the first time in years. After winning four consecutive Frauen-Bundesliga titles, Germany’s reigning champions currently find themselves trailing Bayern Munich in the league, with the Bavarians having won all 16 of their matches played thus far.

Given Wolfsburg have only dropped five points, it would be harsh to suggest the loss of Harder has played a significant role. However, with there being huge disparities in quality between the teams at the top and at the bottom of the table, it’s in Europe where Wolfsburg’s mettle will truly be tested.

Harder tends to operate just behind the strikers for Chelsea, exploiting pockets of space and punishing lapses in defensive concentration to great effect. Wolfsburg are yet to concede a goal in the Champions League knockout rounds this campaign, so Harder will need to employ every inch of her guile and insider knowledge to pick holes in their watertight defence.

While there’s no guarantee she’ll be successful, the effort taken to stymie Harder’s game often leads to more chances for Kirby and Kerr, as we’ve seen countless times this season already. Something that will have Wolfsburg on red alert.

With the Blues also currently on course to retain their WSL crown, holding a narrow two-point lead over Manchester City, Hayes could well lead Chelsea to a historic treble — a feat that would arguably mark the best season in the club’s history. Not bad for a coach only deemed good enough for AFC Wimbledon.

Should the Blues be successful in toppling Wolfsburg, it will be the clearest indication yet that Chelsea have evolved from the best team in England to one that can genuinely threaten Europe's elite.

Catch Chelsea’s first leg clash with Wolfsburg live on BT Sport this Wednesday. Kick-off is at 4pm with coverage beginning from 3:45pm.