London - England flanker James Haskell will miss the first two matches of the champions' Six Nations title defence after being banned for a dangerous tackle while playing for Wasps in a European club match against Harlequins.
Haskell was sent off in Wasps' dramatic 33-28 defeat by English rivals Harlequins on Saturday for a shoulder-led high tackle on Welsh centre Jamie Roberts.
Wednesday's decision by a European Professional Club Rugby independent disciplinary committee saw the red card upheld and Haskell, 32, given a four-week ban that leaves him free to play again on February 12.
That means he will miss both England's Six Nations opener against Italy in Rome on February 4 and the following week's clash with Wales at Twickenham.
Haskell's ban leaves England without two experienced back-row forwards, with Billy Vunipola set to miss the entire tournament after fracturing his forearm in title-holders Saracens' 15-15 Champions Cup draw with the Ospreys -- only his second game since returning from three months out with knee trouble.
England coach Eddie Jones, who is due to name his Six Nations squad on Thursday, will now have to reshape his back-row and loose forward bench cover.
Wednesday's hearing in London decided the 75-times capped Haskell had committed a "mid-range" offence under World Rugby rules, with six weeks the suggested "entry-point" ban.
But taking into account Haskell's record, his guilty plea and early expression of regret, the committee reduced the punishment by two weeks before imposing a four-week ban.