William Zillman was superb in the second half of the Titans' win over Penrith.

The immediate playing future of Titans captain William Zillman remains unclear with a nagging calf complaint again keeping him out of the team to play his former club in Round 4 in Canberra on Saturday.

The only change to the Titans team that defeated the Wests Tigers 30-18 last weekend is the addition of Eddy Pettybourne to an extended bench but he is more likely to return from a cork playing for Burleigh in the Intrust Super Cup.

John Olive gets another shot at right centre due to the shoulder injury that will keep Nathan Davis sidelined for at least another fortnight and Zillman's absence allows David Mead to play his fourth consecutive game at fullback.

Having missed the majority of last season with a back injury that eventually required surgery, Zillman was guaranteed the No.1 jersey in the pre-season before injuring his calf at a training camp in Ballina and then aggravating it in a trial against the Rabbitohs.

He has been a week-to-week proposition ever since but Titans coach Neil Henry refused to speculate on when he could be expected to rejoin the top squad.

"It's really annoying him, he's very frustrated," Henry said.

"He hasn't been able to put together a full week's training and he hasn't been able to do any contact either so until he can do that he's not going to be able to play.

"We thought it was going to be right by now but it hasn't been so I'm pretty reluctant [to put a timeframe on it].

"His volume's been increasing with his running but he hasn't done any contact. It could be the following weekend against the Broncos or the week after that [against the Sharks].

"It's been something that's been ongoing and he just hasn't been able to get it right. He'll run about eight kilometres in a game at fullback and it's not a position you can interchange easily."

In Zillman's absence Mead has been averaging more than 150 running metres per game and has made seven tackle breaks with his hard running.

Mead showed by letting a bomb bounce that led to a try against the Tigers last week that his positional play remains a work in progress but he gets at least one more opportunity to prove he deserves the position on a permanent basis.

Although Zillman has been restricted to just 42 games for the Titans over the past four seasons due to injury, Henry still believes his body is capable of withstanding the physical demands put on the modern day fullback.

"He's a really fit guy and he handles any training at volume normally," said Henry, who was named Dally M Coach of the Year when at the Raiders in 2008.

"He's had a very good pre-season to a point but this has just been a niggling injury that hasn't gone away.

"I don't think it's back related, I think it's just something that he's picked up and hasn't been right.

"He needs to be able to get through the volume, he needs to have that strength and confidence back and he needs to do some contact work so he needs to be part of our opposed sessions.

"At the moment he hasn't done that so he can't play and 'Meady' will be in that spot."