Once a staunch critic of the breakway Saudi-backed series, Rahm has signed up with LIV on a deal reported to be worth up to £450m.
It serves as another blow to the PGA Tour, with Rahm one of golf biggest current stars and a leading voice for the sport.
The Spaniard had previously said that he did not like LIV’s 54-hole, no cut tournament format, while also suggesting that the monetary rewards on offer “would not change” his lifestyle.
McGinley, a four-time winner on the European tour, has criticised Rahm’s apparent hypocrisy.
“So many people have completely reversed their position,” the Irishman told Sky Sports. “Jon came out very, very strongly in support of the tours, and came out very strongly that this was not a good format, that he didn’t enjoy it, he didn’t see any future in it.
“[He said] he was chasing his own career and titles on the PGA Tour and DP World Tour, and obviously the Ryder Cup. He knows that, by going here, it’s going to put a lot of that in jeopardy.
“Whether it does or not, we’ll have to wait and see. It’s a complete reversal of the position that he has stood very strongly on. A number of players who have gone over to LIV have done the same thing — they’ve said one thing and then done another.
“Who do you believe any more? You can’t take anyone’s word any more because people reverse their positions quickly and, it seems, pretty easily.”
Rahm’s move comes amid discussions over a possible partnership between LIV and the two established tours.
The PGA and DP World organisations announced earlier this year that they would discuss a merger, with a deadline of the end of the year set to conclude a deal.
McGinley wonders if Rahm’s defection suggests that an agreement is not close.
“I’m not involved in these high-level discussions that are going on,” McGinley said. “There is rumoured to be a deal, and I think ultimately there is going to be a deal. I’m hoping that the game will be unified again at some stage.
“Is there enough room in the schedule for the players to play 14 or 15 events, and still play 14 or 15 events between the PGA Tour, DP World Tour and Ryder Cups? No — the players don’t want to play 30 tournaments a year. It is a very crammed situation now.
“I’m hoping there is going to be a deal. I thought we were going to do a deal with Saudi and there was going to be an announcement, but obviously that has taken a turn for the worse. Saudi probably didn’t think things were going their way to get an agreement together, so they have brought out the chequebook to put things in their favour.”
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