It would be a lot different than Favre retiring. Favre unretired 5 weeks before the next training camp. Technically, he barely missed a practice. And he never fully committed to retiring, never once telling the Packers that he was sure he was going to retire.

OTOH, Armstrong has missed 3 years of competitive racing.

What makes it more difficult for someone like Lance to unretire is that he probably wouldn't be satisfied with a 10th place finish in the TdF. Most athletes can slip a bit and still be satisfied. Say a baseball player who hit .310 with 40 hr in their prime, but in their later years slips to .280 w/30 hr. Or golfers that slip from winning 3-4 tournaments a year to having the occasional top 5 finish & rare win.

That's a problem for Favre too. He can't gracefully slide from being the ace pitcher to being an effective #4 starter for his last couple of years. He's got to be a starting NFL QB leading his teams to wins.

Lance could come back and compete for top 10 finishes or wins in minor races. Or compete for age group titles. But I'm not sure that would be enough for him. He'd want to make a run at major wins. At least that's my impression. I could be wrong.

He could be the catalyst for creating great interest in Master's events. Much like golfers like Arnold Palmer made the PGA Senior Tour more significant.