Some players have to go away to come back to Ireland and not always to their home province.
Take Eoin Reddan - Munster to London Wasps to Leinster. Take James Downey - Leinster to Northampton to Munster.
There are a limited number of seats for the return flight to one of four provinces.
Where Leinster have taken State of Origin Rugby League hardman Ben Te'o, they could have made a move for London Irish centre Eamon Sheridan, a midfielder of uncommon size in Irish rugby at 6'4" and 17 stones.
"Ben looks like a good signing for Leinster. Looking at him playing League, he is a big, physical, power runner and if he can make the transition, he will be very good for them," said Sheridan (inset).
The truth is injury did the Navan man out of a shot at his natural berth at twelve for his home province.
A bad knee injury, a broken leg and serious hip problem combined to make him redundant for the best part of two and a half years.
Sheridan played three times for Leinster in four seasons.
"I was really disappointed to have to leave at the time," recalled Sheridan, speaking at the announcement of a new marketing partnership between Setanta Sports and London Irish rugby club.
From there, Sheridan flew to the unfashionable Rotherham Titans, where one season free of injury playing in the English Championship allowed him the time to improve.
"It really worked for me. My luck changed. I got a run of games, playing 22 matches. That was huge. It brought my game on a lot," he said.
His form was not lost on London Irish. Contact was made. A two-year contract soon followed. He wore 20 caps for the club in The Premiership last season, concussion and a broken hand preventing him from adding to those.
An extended contract is in the pipeline.
"The step-up into The Premiership, compared to Leinster's PRO12 League, was slightly more physical, but slightly slower," he noted.
"I have made improvements. I've been working a lot on my decision-making and my skills, just adding the subtleties to my game," he said, pointing to former Ireland kicking coach Mark Tainton as one of the main reasons behind his progression in those areas.
"Leinster is my home. But, I have been pretty happy with how things have gone since I left.
"Wherever I can get game time is where it is going to suit me best. Right now, that is at London Irish."
The grass is not always greener in Ireland.