Blues' bid to dethrone champions boils down to a question of control
Leinster will take some beating today. They have to be favourites on the basis of the rugby they have played this season, and given the experience their plethora of Ireland internationals have just been through with the Six Nations. They will have returned from that camp on cloud nine. But - and it's a big but - if there was one team they would not have wanted to face in the quarter-finals, it would have been Saracens. This stage of the competition, when teams are trying to regroup and re-integrate a significant number of players after the international break, favours the teams with the strongest cultures.
And at club level that is probably Leinster and Saracens (and Munster). Mark McCall's team have been here before. They have won the last two Cups. They travelled to the Aviva last year and beat Munster in the semis with one of the most professional performances I have ever seen from an English team abroad. Saracens have not played as well this year, but they have the capability to do so again. This is not England v Ireland, as some have billed it. This is the two-time European champions chasing a hat-trick. They know what it takes. That experience gained, not just of tactics but of "feelings" and attitude, stays with you.
Maro Itoje and Owen Farrell must exorcise their demons from the Six Nations
I was fascinated by the two teams' contrasting approaches to last weekend's games. Leinster had the Ospreys away in the Pro 14. They chose to rest their stars, travel to Wales with a second-string outfit, and they got beaten. Fair enough. I think it was the right call. The likes of Johnny Sexton, Tadhg Furlong, James Ryan, Dan Leavy and the rest are not going to have lost any sharpness in the past two weeks.
They are playing with enormous confidence. A really sharp week of training this week and they will be bang up for it. McCall had a different dilemma. Given the way England finished the tournament - with three straight losses - he needed to give at least some of his internationals the chance to get some momentum going. He named a strong team to face Harlequins, they got the win, and I thought Maro Itoje, in particular, had a big game. The question is, after those contrasting approaches, who will carry the most momentum into this game?
The key battlegrounds
Owen Farrell's recovery from a quad muscle injury to make the starting line-up is a massive boost. I like Alex Lozowski a lot and know him well from his time at Yorkshire Carnegie. But Farrell is a big-match player, and up against Johnny Sexton - another big-match player - that is what you need. The kicking battle, and particularly the kick-chase, will be huge today and having the Richard Wigglesworth-Farrell combination is definitely a psychological boost to Saracens.
With George Kruis also passed fit, Mako Vunipola shaking off a knock, and Brad Barritt playing with a metal plate in his cheek, Saracens are showing just how desperate they are to get their big guns out. They will need their attitude as much as their skills to play a team very well coached and who are tactically so astute.
There are huge head-to-heads, not just one-on-ones but unit v unit, none more so than in the three forward units. Leinster have an exceptional front row, both technically and in phase play involvement; Mako Vunipola, Jamie George and Juan Figallo will have to match this. In the second row Kruis is the best organiser of a line-out. Davin Toner and James Ryan will be tactically challenged by him and Itoje, and line-out efficiency plus turnovers can determine the territorial advantage.
In the back rows, another fascinating battle, encapsulated by "old head" Schalk Burger against "young gun" Dan Leavy, who was close to being my man of the Six Nations. And who waits for all these little edges to show - messrs Sexton and Farrell, two of the three best 10s in world rugby.
McCall's team must cope better than Exeter did with Leinster breakdown
I think what both Leinster and Ireland have shown this season is that Irish teams are a real force at the breakdown just now. And I think this area is going to be so key.
The Irish just seem to have a much clearer decision process around the breakdown; when to speed it up, when to slow it down, how to do both. There is a clarity about their play, everyone knows his role. I thought Stuart Lancaster's team out-thought as much as out-fought Exeter over their two legs in December. Exeter like to go through the phases, put two men at the breakdown and recycle the ball quickly. Leinster flooded the breakdown, sometimes putting as many as five men in, a tactic replicated by Scotland and Ireland in the Six Nations.
Ultimately it will boil down to which team can control it
Saracens have evolved from being a strong defensive team to one who can switch it up, who can counter-attack and offload through good decision-making. They demonstrated that devastatingly in Dublin last year in that 26-10 semi-final victory over Munster, when they soaked up everything the Irish province threw at them, and then blew them away in the final quarter. That ability to soak up pressure, control the game and react to what is happening will be so important. I will be fascinated to see where the game is played.
Saracens are very good at getting the ball into their opponents' half and staying there. Leinster are more flexible in where they are prepared to attack from, but Sexton will be putting them in the right places. Both teams' kicking game will be important, and that comes back to those essential edges up front. Who will give their 10 the best and consistent possession at key moments, because outside them are more match-winners and finishers, Garry Ringrose and Liam Williams to name but two. There is the rub, and the winning.