Cyrus Christie is ready to step into the heat of World Cup battle if Republic of Ireland boss Martin O'Neill needs him.

O'Neill has spent much of the last week keeping a watchful eye on Everton full-back Seamus Coleman, who has not played a single minute of competitive football for his club this season because of an ankle injury.

Coleman's would be one of the first names on the Ireland teamsheet for Monday night's opening qualifier against Serbia in Belgrade (7.45pm, live on RTÉ2) if he were fit - indeed, he ended the Euro 2016 finals wearing the captain's armband - although assistant manager Roy Keane admitted on Friday that he remains a doubt.

Should he miss out, Derby counterpart Christie would be the natural replacement, and he is desperate to prove O'Neill's confidence in him is well-founded.

The 23-year-old said: "The manager does have faith in me to play and if I need to be called upon... It's just a waiting game.

"When we were away at the Euros, he came up to me and said I deserved the chance to play, but he couldn't really fit me in the team at that moment and just to look forward to the World Cup qualifiers.

"To hear that from the manager is great and you can come away happy even though it's frustrating that you're not playing.

"It was a fantastic experience just to be there and I can take a lot away from that and a lot of memories. It was a great experience for me."

Christie has already played competitive football for his country - he started the victories in Gibraltar and at home to world champions Germany on the road to France - but his appearances to date have been mainly in friendlies, the latest in Wednesday night's 4-0 win over Oman.

He said: "I have got Seamus in front of me, who is a fantastic player, but for me every time I go out there, it is an opportunity to prove myself."

The squad flew out from Dublin on Saturday afternoon with O'Neill still sweating on Coleman's fitness, and Christie was preparing to be thrown in at the deep end if required.

While he watched from the bench this summer, he too can take confidence from the way the Republic performed.

However, no-one within the camp is underestimating Serbia, who were disappointing in their last qualifying campaign, but will be a handful at the Crvena Zvezda Stadium as they launch a new one.

Christie said: "Now our focus will go on to Serbia. We can only take it one game at a time. It's a big game on Monday and we'll look forward to it.

"We need to take confidence from the campaign we have just had in the Euros. We will concentrate on Serbia now and we will go into that game full of confidence.

"You always want to get off to the best possible start and we need to lay our marker down. It's going to be a tough place to go and we need to take the confidence from the Euros and just play our game.

"On our day, we are a handful for anyone."

Both teams will be depleted by suspension with Ireland defender Shane Duffy missing as a result of his red card in the 2-1 finals defeat by hosts France, while the Serbs will be without Aleksandar Kolarov and Nemanja Matic, who were both dismissed as they went down 2-1 at home to Portugal in their last Euro 2016 qualifier.