After leading the line for the Republic of Ireland Under-21s in their UEFA Championship qualifying campaign to date, Celtic striker Cillian Sheridan is thrilled to have received his maiden call-up to the senior squad.

The 21-year-old took part in his first training session on Sunday at Gannon Park and is hoping to impress enough in this week's training camp to win a place in the panel for next week's double-header of friendlies against Paraguay and Algeria at the RDS.

The Cavan native, who scored six times at SPL club St. Johnstone while on a loan spell for the second half of the campaign, was not named by Giovanni Trapattoni in the original 23-man squad but admits to being ecstatic when some injury withdrawals went in his favour.

"It was definitely a surprise to get the call-up," he said on Sunday evening. "The call came after the last St. Johnstone game of season (two weeks ago). I hadn't actually played in that match which was a bit disappointing but to get a call-up like this made up for it.

"I had planned to attend to FA Cup final at Wembley on Saturday and obviously couldn't go but I definitely prefer to be here with the Irish squad."

Working with Trapattoni and his staff on his first day at training was an eye-opening experience for Sheridan.

"It was the first time working with the manager and he's different to what I was used to in any of Ireland set-ups at underage level," he said.

"It was really good and I enjoyed the training. At the beginning of the session, he (Trapattoni) welcomed all the new players and said he was going to be having a good look at us this week."

Trap will utilise Tuesday's training game against the Republic of Ireland Under-23 squad to assess his newcomers and Sheridan is just one of the many rookies intent on laying down a marker.

He said: "The main aim of this whole training week is to impress the manager enough to make the squad for the two friendlies next week. If I can do well on Tuesday, maybe I could get a chance in the next week and once you're in the squad, you never know what can happen from there."

In squad news, David Meyler (Sunderland), Darron Gibson (Manchester United), Stephen Ward (Wolves) and Caleb Folan (Hull City) are ruled out while Keith Treacy of Preston North End returned to his club on Sunday for treatment after having his hernia injury assessed.

Marc Wilson (Portsmouth) and James McCarthy (Wigan Athletic) are carrying knocks too and, having not assembled with the squad as yet, a decision on their availability will be made in due course. Uncapped Manchester City full-back Greg Cunningham has been added to the squad and trained on Sunday.

- Tickets for the Republic of Ireland's senior international matches against Paraguay on May 25 and Algeria on May 28 in the RDS, are on sale through www.fai.ie and the FAI Umbro store in Carrolls, Westmoreland St, Dublin.

Schoolboy/girl tickets for both games are also being made available for €10 through schoolboy/girl leagues. Kick off for both games is 19.45hrs.

Two match ticket, North and South stands €65. Two match ticket, Anglesea / Grandstand €85. 

- By purchasing tickets for the Algeria/Paraguay Internationals you will automatically be guaranteed the right to purchase tickets for the opening football game in Aviva Stadium, when Manchester Utd take on our Airticity League XI on August 4.

When purchasing your Republic of Ireland tickets, you will be asked to leave your e-mail address and you will be contacted before general sale of the Airtricity League XI v Man Utd game with a first option to purchase tickets.