Patrick Mahomes had someone unexpected beside him during the loneliest part of his recovery

Less than 24 hours before undergoing major knee surgery of his own, Zach Ertz picked up his phone and sent Patrick Mahomes a message.

He had just watched the Kansas City Chiefs quarterback suffer a devastating non-contact knee injury against the Los Angeles Chargers. Ertz knew immediately that Mahomes was about to enter a world he understood all too well.

The veteran tight end had already been through an ACL recovery earlier in his career. Now, after suffering another serious knee injury just a week before Mahomes, he was about to do it again.

So Ertz sent Mahomes a simple message.

"It's a lonely road ahead," he told him, while making sure Mahomes knew he would be there if he needed him. Neither man could have known how important those words would become.

Mahomes and Ertz suddenly had each other

The timing was remarkable.

Mahomes and Ertz underwent ACL and LCL repair surgeries on Dec. 15. They weren't teammates and didn't even rehab together, but suddenly they were going through almost exactly the same physical and emotional battle at the same time.

They began texting. How is rehab going? What did you work on today? How are you getting through it?

The messages weren't about football fame, Super Bowls or statistics. They were two injured players trying to make it through days when progress could feel almost invisible.

For Mahomes, that mattered.

The Chiefs quarterback later admitted that rehab can become incredibly lonely because so much of the work is done by yourself. Ertz gave him someone else to measure himself against and another outlet for the competitive drive that normally has an entire football field to feed it.

For Ertz, Mahomes provided something equally valuable: proof that it was possible to keep pushing.

One Mahomes video changed something for Ertz

Knee rehabilitation doesn't always reward effort immediately.

Ertz explained that an athlete can spend days working on an exercise without being able to add even a pound because range of motion simply isn't there yet. For players accustomed to measuring improvement constantly, that can become mentally exhausting.

At one point, Ertz was hesitant to attempt crossover steps. Then he saw Mahomes.

A video showed the Chiefs quarterback already performing the movement as he dropped back to pass . Watching Mahomes attack that stage of his recovery gave Ertz the confidence to push himself, too.

"I think he just encouraged me," Ertz told The Athletic, pointing specifically to how aggressively Mahomes approached his rehabilitation. But this wasn't a one-way relationship.

Ertz had something Mahomes needed, too

At another point in the process, Mahomes was having difficulty pushing off his big toe while running. Ertz knew the feeling because he had experienced the same problem.

So instead of simply sending encouragement, he sent Mahomes an exercise and a video showing something that had worked for him. That small exchange perhaps explains their relationship better than anything else.

They weren't just telling each other everything would be OK. They understood what the other was feeling because, in many cases, they had felt it themselves.

When one found something that worked, he shared it. When one moved forward, the other saw what might be possible.

And when Mahomes was finally cleared to participate fully in Chiefs training camp barely more than seven months after surgery, Ertz was watching. "Bro, you're killing it," he texted him.

Mahomes barely looks like he was injured

Mahomes' progress has become increasingly visible.

After tearing the ACL and LCL in his left knee in December, the three-time Super Bowl champion worked his way back to full participation at training camp in late July, an extraordinary milestone given the severity of the injury.

Ertz said that when he watched Mahomes during offseason work, there was almost nothing in his movement that suggested what he had gone through.

The knee brace was the giveaway. Without it, Ertz said, Mahomes looked like Mahomes. That comeback carries even more meaning for Ertz because his own journey isn't finished.

At 35, the veteran tight end is training at Stanford while waiting for another NFL opportunity. He says GPS data has his top speed back to 99 percent of what it was before the injury, while other testing has shown encouraging improvements in his explosiveness and strength.

Ertz believes he can still help an NFL team. He isn't asking to be promised a starting job or a specific role. He just wants the opportunity to compete.

And somewhere along a recovery that began with uncertainty about whether he had played his final NFL snap, he found an unlikely person helping him believe that was still possible. Mahomes did the same.

Two players in different places, working for different teams and facing different futures somehow ended up sharing the same difficult road. Ertz's first message to Mahomes turned out to be right. Rehab could be lonely. They just didn't have to go through it alone.