Bishop-elect Fr Kieran O'Reilly (57), who has lived in Rome since 2001 as Superior General of the Society of African Missions, said that he was surprised by his promotion.
But he expressed his gratitude to the German Pontiff for being assigned to "this ministry of service and leadership in the Church of Killaloe".
Pope Benedict's decision represents a snub to the views of the Killaloe diocese's 100 priests who, earlier this year, conducted a vote on who should succeed Bishop Walsh.
Bishop Walsh confirmed that the terna -- a list of three candidates from the diocese -- did not include Fr O'Reilly "because the priests didn't know him".
Resignations
Fr O'Reilly's elevation is part of a process under which Rome is putting its conservative stamp on the Irish bench of bishops and ignoring local diocesan opinion.
Recent high profile resignations have come in the wake of the Murphy and Ryan inquiries.
These include the departures of James Moriarty from the diocese of Kildare and Leighlin, Bishop of Cloyne John Magee and former Bishop of Limerick Donal Murray amid intense criticism of their handling ofchild abuse allegations.
Bishop Joseph Duffy last month stepped down as head of the Diocese of Clogher and Bishop Francis Lagan retired as auxiliary in Derry after they both reached 75.
But the future of Dublin auxiliary bishops, Eamonn Walsh and Ray Field, who offered their resignations last Christmas Eve in the wake of the Murphy Report, has not been revealed.
Bishop Walsh said that Fr O'Reilly's appointment was a surprise "as I didn't know the man". He confirmed that he was told of it two weeks ago.
"Yes, I was surprised. I suppose it is always human to think or to hope that the man appointed might be someone you know. Somebody as it were 'of our own' and we did have a number of men who were quite capable of leading the diocese."
However, Bishop Walsh said that "there are a lot of advantages to a person from the outside coming in with new and fresh ideas and carrying no baggage".
Bishop Walsh said that he spoke to a number of priests from the diocese yesterday "and they are warmly welcoming the appointment".
Privilege
"I am very happy with Fr O'Reilly's appointment," said Bishop Walsh, adding that "it is my hope and prayer that his particular experience of evangelisation in a younger African church will bring new life and rejuvenation to an older Irish church".
Fr O'Reilly admitted that "it is going to take time to understand all that is involved in being a bishop, it will be a great privilege to serve in Killaloe".
Educated at Presentation Brothers, Scoil Chriost Ri and Colaiste Chriost Ri in Cork and St Patrick's College, Maynooth, Fr O'Reilly was ordained for the Society of African Missions in 1977 and has dedicated his life to the missions.
Bishop Walsh will remain on as bishop until he takes over at a ceremony in Ennis in late August or early September.
SIC: II