England prop Joe Marler has been ruled out of Harlequins’ Investec Champions Cup clash against Cardiff as his arm injury continues to be assessed.

It comes amid front-row concerns for England head coach Steve Borthwick ahead of the Guinness Six Nations.

Marler’s fellow loosehead props Ellis Genge, Bevan Rodd, Mako Vunipola and Val Rapava-Ruskin are also on the sidelines.

Borthwick’s problems include a four-match ban being imposed on Saracens’ Vunipola, who was sent off for a dangerous tackle against Premiership opponents Newcastle.

Although he will be available if required for the Six Nations, experienced campaigner Vunipola cannot play again until after Saracens’ Premiership appointment with Exeter, which is only a week before England’s Six Nations opener against Italy on February 3.

Genge, an England captaincy contender following Owen Farrell’s decision to miss the Six Nations, last featured for his club Bristol on December 2. He has been sidelined due to a hamstring injury.

Sale forward Rodd is out for the rest of this season after undergoing toe surgery and Gloucester’s Rapava-Ruskin, who was part of England’s World Cup training squad last year, is another long-term absentee following a knee operation.

On the 88-cap Marler, who was hurt during Quins’ victory over Gloucester 10 days ago, the club’s head coach Danny Wilson said: “There is still a little bit of assessment going on.

“Joe is a week-by-week process at the moment to make a full assessment of the time period and the time-frame.

“He is not going to play this weekend – that is pretty clear – but what I can’t give is a time-frame. There have been a few twists and turns with it.

“We are kind of in the middle of a full assessment.

“I know that is going to sound a little bit like it is taking a while to assess, but there is a little bit to this one so I am probably not really going to be able to give you much.

“Until we get a full picture and a full time-frame, and we are in that process at the moment, then I can’t really tell you a huge amount.”

Will Stuart hopes involvement in Bath’s resurgence this season can help in his quest to become England’s first-choice tighthead prop.

The 27-year-old was delighted to go to a first World Cup earlier this year but frustrated at starting just one match at the showpiece in France – the Bronze Medal victory over Argentina – and being left out of the 23-man pool entirely for the knockout clashes against Fiji and South Africa.

As he enters what he hopes will be his peak years, Stuart is determined to stake a strong claim to take over from 36-year-old Dan Cole and become England’s established number three in time for the next World Cup in Australia in 2027.

The former Wasps forward – who has won 33 caps since his debut against France in the 2020 Six Nations – threw himself straight back into club rugby after the World Cup and has helped Bath make a strong start in both the Gallagher Premiership and the Investec Champions Cup.

“Every player wants to play in a World Cup and the next one in Australia is a massive goal for me,” Stuart told the PA news agency.

“If my career ended now, I’d say ‘I achieved a little bit, I won a few caps for England and played at a World Cup’ but realistically I haven’t won silverware, I haven’t played in multiple World Cups and I haven’t really solidified myself as a starting tighthead for England, so there’s a lot I aspire to do.

“I played in three of the group games (as a substitute) and then missed out on the quarters and semis, which was a frustration.

“But it’s been pretty clear from chatting with the coaches what my work-ons are and what I need to do to be a first-choice tighthead for England.

“If I’m playing well for Bath and can contribute to a winning team, that falls into giving myself a good opportunity to push on with England as well.”

In addition to his own form, Stuart’s bid to establish himself for England will be influenced by how long veteran Leicester tighthead Cole can soldier on.

“The way Coley plays, I reckon he could play until he’s 54,” joked the Bath forward. “He’s great, he was great for me during the World Cup and it’s impressive that he’s still playing at that level at 36.

“He’s on 107 caps for England and played 300-plus games for Leicester and he’s been starting and playing 70-odd minutes for the majority of that so he’s a good person to look up to.”

With the Six Nations looming in the new year, Stuart feels England have huge potential for further growth under Steve Borthwick after defying pre-tournament scepticism to reach the World Cup semi-finals.

“I think we were written off a lot during the World Cup,” said Stuart.

“Draw-wise we probably had an easier route to the quarters but we ended up taking South Africa to one point in the semi-final and until the last 20 minutes we were all over them, so I think that is something to massively build on.

“Including the Six Nations and the lead-up to the World Cup, the coaching group probably only had about a six-month period to really work with the team and, with that in mind, we had a way of playing where we knew we could basically get to knockout rugby.

“When we got to that stage, it was always going to be fine margins and we were one point away from the final.

“I think the coaches have been very clear on the areas where we can push on and make massive strides to get back to where England have been in the past.”

Owen Farrell will make his first appearance since his decision to step away from Test rugby was announced when Saracens launch their Investec Champions Cup campaign on Saturday.

England captain Farrell will be unavailable for the Six Nations later this season after choosing to take a break from the international game to prioritise his and his family’s mental well-being.

He then missed Saracens’ Gallagher Premiership defeat against Northampton due to a knee problem.

But Saracens rugby director Mark McCall has confirmed the 32-year-old fly-half will face leading South African challengers the Bulls in Pretoria.

“He’s available and he is going to play this weekend,” McCall said. “He has trained fully over the last two days.

“He has enjoyed being with his team-mates, and it is a great opportunity for us all to spend a bit of time together away from the British winter.

“I don’t know how many European Cup games he has played – him and Alex Goode have probably played in more than anybody at the club.

“He is our captain, he is our leader, someone who is respected by everyone at the club. To have him on the field, of course, is an enormous benefit.

“Not just to have him on the field, but have him in the team-room, in the meetings… His contribution is so enormous and it is great to have him here with us.”

Three-time European champions Saracens have won the tournament more than any other English club, although they made a quarter-final exit last term to eventual winners La Rochelle.

And they will tackle a Bulls side currently third in the United Rugby Championship, having won five out of seven league fixtures this season.

McCall added: “We have been really impressed with what we have seen, especially in their last couple of home games. They are strong in all areas.

“Games don’t get much tougher in round one than coming to the Bulls, especially with the run of form they are on, but it is a challenge which usually brings the best out of the group we have got.

“We’ve had a good relationship with this competition for a very long period of time. It has felt really good on the training field from the moment we touched down here.”