The Blues have been beset by unfamiliar challenges this week in the run up to a crucial FA Cup semi-final slug-out with fellow title contenders Tottenham Hotspur, in a period that is setting up to be the most daunting test of West London side's mentality. Exactly how strong is that mentality?Barely a few weeks ago the Blues looked on top of the world; heads and shoulders above the rest of English football, 10 points clear at the top of the Premier League table and looking forward to a spicy FA Cup semifinal tussle with second placed Tottenham Hotspurs. That much-hyped tussle indeed arrives as the sun rises above the width of Wembley. On the west side of London a cloud of perplexity over the events of the last week or so. Chelsea are no longer in the best of moods, it seems. Two losses in four league matches and they are now a paltry 4 points away from the day's opponents, and with a whopping 6 games yet to play. Chelsea found themselves deflated and dragged through the dirt in their forgettable defeat at Man United last time out. It was their worst performance since losing to Arsenal in September. Not a single shot on target??? Yeah, how many times has that been said already? Not enough! READ ALSO: What does Marcos Alonso offer Chelsea?They take on a Spurs side in the hottest streak of form; on the back of 8 straight league wins. They meet the only side that currently stands between them and double glory in the most foul of moods.Chelsea are not in seven heaven anymore. In the past week, they have had to play with a disrupted formation following the enforced absences of Thibaut Courtois and Marcos Alonso. They have also had to deal with the news of John Terry's season end departure. All these amidst sticky rumours surrounding the future of Eden Hazard. With such an important fixture to negotiate, there are health concerns around not less than four of their players, including Marcos Alonso, Thibaut Courtois, Victor Moses, Diego Costa and, of course, stand-in captain Gary Cahill, who is reported to be an almost certain miss. Should Chelsea be worried about Spurs surge?Chelsea are hurt, for sure. It is a precarious situation that they have not had to face before throughout this season. This is the time that their mental strength is being most keenly tested. The question is, how do they respond to what's in front of them? As deserving champions wannabe or as the foot that stuck to the mud. So, which Chelsea will show up against Spurs? A wounded lion... or a wet-feather cock?