The answer was simple: Winning.
So when a team owner synonymous with winning put an offer in front of him, Montoya snapped at the opportunity. He'll leave NASCAR behind for a return to open-wheel to drive for Roger Penske—the IndyCar Series rival of Montoya's longtime boss, Chip Ganassi.
"He's very excited for me," Montoya said Monday after texting with Ganassi, who is in Europe. "Something that we have with Chip is that we're very good friends. We have a lot of respect for each other. He had to make a decision this year to go in a different direction. I had to do the same thing. I had an opportunity and a great chance with Penske. We're going to be competitors and I'm looking forward to the challenge."
Ganassi decided in August not to bring Montoya back next year to his NASCAR program. It put the Colombian on the free agent market, and even though Ganassi has said he'd not ruled out using Montoya in his other programs, Montoya considered everything.
He spoke with Michael Andretti about an IndyCar ride, and Furniture Row Racing about replacing Kurt Busch at the end of the NASCAR season. There were calls to Europe, and a new rumor about a possible test with Lotus in Formula One.
Then came discussions with Penske and all bets were off with the other teams.
"My No. 1 choice was going to be in a winning car. I really wanted to be in a winning car," he said. "It came down to I wanted to race for Roger. In a way it's always been one of my dreams to be able to be part of his organization. Being here, it's unbelievable. I'm so excited. I'm like a 5-year-old kid right now."
Some could also consider the move a big piece of gamesmanship in the racing rivalry that spans two series between Ganassi and Penske. Castroneves and Ganassi driver Scott Dixon are currently locked in a fierce battle for the title, and the competition has heated up over the last two races as Dixon has been involved in incidents with Power and the Penske organization.
"He's a great driver and deserves a great drive," Ganassi told The Associated Press. "He will have that there at Penske Racing."
Montoya won the 1999 CART title, the 2000 Indianapolis 500 and 11 races driving open-wheel for Ganassi. He then moved to Formula One, where he had seven wins and 30 podiums, before reuniting with Ganassi again in 2006 to compete in NASCAR.
But results in NASCAR have been sporadic. Montoya has just two wins in 244 career starts and his best season finish was eighth in 2009. He's 20th in the standings this season.
The program has been through several rebuilds since Montoya came aboard, and it was a middle-of-the-road organization when he signed on in 2006.
Their first NASCAR season was decent and gave the organization a boost with a win on the road course at Sonoma, six top-10s and rookie of the year in 2007. But 2008 was the first sign of trouble as Montoya had two crew chief changes in the first 16 races.
Montoya made the Chase for the Sprint Cup championship in 2009 with crew chief Brian Pattie behind a career-best 18 top-10s, and he was third in points with six races to go in the season before fading to eighth in the final standings.
He won on the road course at Watkins Glen in 2010, but Pattie was let go before Indianapolis in 2011 for Montoya's fourth crew chief change. The Ganassi team began another overhaul that winter and Chris Heroy was hired as Montoya's fifth crew chief before 2012. That entire season was spent trying to get the Ganassi cars up to speed.
With the hiring, Montoya is now stuck in the middle of a spat between Penske and Ganassi drivers over in IndyCar.
Ganassi driver Dixon was penalized in Sonoma when his car made contact with a crew member for Power, Castroneves' teammate, on the final pit stop. IndyCar race director Beaux Barfield said Dixon had driven into the Penske Racing work space, but Dixon alleged the crew member walked into his car.
The penalty cost Dixon a chance to race for the win, and opinion was split through the paddock as to who was at fault and if race control perhaps should not have penalized anyone.
Dixon and Power collided at the next race at Baltimore, and the contact ended Dixon's day when IndyCar officials did not tow his car back to pit lane for repairs. He then said Barfield should be fired, comments that earned him a $30,000 fine from IndyCar.
Montoya said he'll try to stay out of the fray.
"I think I'm going to have a little white flag, I'm going to be very neutral there," Montoya said. "For one side, I'm still committed with Chip and the NASCAR program for the next nine races. But I think it's going to be fun. It's going to be like mixed emotions watching the last few IndyCar races."