1 Liam Mitchell (Zebre Parma) 46

The 26-year-old lock has made an immediate impression in his first season of European rugby after joining Zebre from New Zealand side Hurricanes last year.

Mitchell has played in all three of the Italian side’s games and helped prevent their three defeats being heavier, missing only six tackles in 52 attempts.

2 Grant Gilchrist (Edinburgh Rugby) 43

Gilchrist is another industrious lock, with the Scotland international even more efficient than Mitchell in defence, having let only two attackers elude his clutches.

The 31-year-old has not missed a minute of Edinburgh’s three games as the Scottish region have moved into second place in Pool 2 and on the verge of qualification for the last 16.

3 Oliviero Fabiani (Zebre Parma) 36

Hooker Fabiani has also been a key defender for Zebre, although he has missed five tackles in his 41 attempts over the Italian team’s three Pool A games.

The Italian international has been a regular for Zebre in European competition for the past eight seasons and has now made 29 continental appearances for them.

Zebre Parma, who prop up Pool A of the EPCR Challenge Cup with a single point, head the competition’s list of tacklers, with four players in the first six.