Andy Farrell says he faces "a tough call" picking Ireland's Six Nations scrum-half - with Ulster's John Cooney "playing some magnificent football".
Munster number nine Conor Murray was consistently first choice under former coach Joe Schmidt, with Kieran Marmion and Luke McGrath regular deputies.
"A lot of things are falling in place for John. He is in a confident mood," Ireland's new head coach Farrell said.
"When half-backs are confident, their game just flows."
He added: "You look at the number nine position and those players are all in good form - it will be a tough call in the end, that's for sure."
Farrell is considering his squad before a Six Nations campaign that begins against Scotland in Dublin on 1 February.
Cooney has been in outstanding form for Ulster, scoring seven tries this season, including crucial scores in all four of the province's European Champions Cup pool games.
Farrell named a 45-man group for the first squad get-together and light training session under his stewardship, which took place on Sunday and Monday at the IRFU High Performance Centre in Dublin, describing it as a "24-hour mid-season stocktake".
The former England rugby league and rugby union international took over Schmidt following the World Cup, having been an assistant to the New Zealander for four of his six years in charge.
"In the last four years with Joe I've learned a hell of a lot and over 20 years of being involved in rugby I've picked up a lot from some fantastic coaches I've been involved with throughout my career," Farrell said.
"I will try and mould all that together and try to put my own stamp on it too."
Door still open for Kearney
Farrell omitted 95-times capped full-back Rob Kearney from his squad for the pre-Christmas gathering at Abbotstown but says the door remains open to the Leinster player and others, such as Ulster back row Jordi Murphy, who were not involved.
"I had a chat with Rob and we want to see a reaction - we want to see a bit of fight. We want to see everyone sticking their head above the parapet and saying 'you have to pick me'," the new Ireland coach said.
"I sense after the camp that everyone is going home to their provinces hungry to be in the Six Nations squad.
"The players are going home knowing what they have to do to get into that squad and that applies to the players who weren't in the camp too."
'We're just looking to get better'
Farrell is confident Ireland can overcome the disappointment of again falling at the quarter-final hurdle at the World Cup in Japan by putting in a serious challenge for the 2020 Six Nations title.
He said: "We can 100% win it. We've made that known as a coaching staff to the players and we're looking to drive forward. There are parts of the game we need to progress with and we're just looking to get better.
"We don't just want to be hard to beat. We've had some unbelievable times in the years under Joe - it has been unprecedented - but we have to capture that and keep pushing forward.
"Is that good enough to win the Six Nations? We sure hope so."