Nacewa was a utility back who played for the Blues in the Super Rugby competition and Auckland in the Air New Zealand Cup.

In the 2007 Super 14 coach David Nucifora trialled him in their first match against the Crusaders at Fly-half in place of first-choice Luke McAlister who was out because of an injury.

[3] According to media reports in October 2009, Nacewa was sounded out about the possibility of again playing for Fiji on their tour to Europe, but he rebuffed these approaches to retain his focus on club rugby with Leinster.

However, he suffered a setback when he sustained a broken arm in the win over the Ospreys on 19 September, a game in which he scored two drop goals.

The Irish Times said of his performance "Nacewa's selection at fullback was vindicated for his stunning line and pass for D’Arcy's opening try.

[6] He retained his place at full-back for the Heineken Cup final on 23 May 2009, keeping Ireland first-choice and Lions tourist Rob Kearney on the bench, and contributed well to Leinster's 19–16 victory.

[4] In the 2010/2011 season, Nacewa established himself as one of the finest full-backs in Europe with eye-catching displays for Leinster in their Heineken Cup run, scoring two tries in the pool stages as well as a brilliant solo effort in the quarter-final against Leicester.

"[7] Nacewa picked up his second Heineken Cup winners medal after playing a key role in Leinster's second-half comeback against Northampton at the Millennium Stadium, Cardiff.

On 20 March 2013, it was reported in the Irish Times that Nacewa would finish his career and return to New Zealand at the end of the 2012–2013 season, despite having a year left on his contract.

In September 2017, Nacewa and teammate Jamison Gibson-Park were denied entry to South Africa due to newly created restrictions that required citizens of New Zealand to obtain a visa.

[16] On 12 May 2018, Nacewa kicked the match-winning penalty in Leinster's 15–12 defeat of Racing 92, in the European Rugby Champions Cup final, gaining a record-equalling fourth win as a player in the competition.