On the eve of what would be his first NFL game, Saturday's preseason affair against the St. Louis Rams, rookie receiver Jeff Janis could not help but think about his father.

As the Green Bay Packers' seventh-round pick sat in his St. Louis hotel room and prepared for his debut, Janis knew it was the anniversary of his dad's death. Christopher Janis died on that day, four years earlier, of liver cancer.

It's been 4 years since I lost my dad. Still to this day I cannot believe it. I know he will be... http://t.co/YW9nwVrDA0 — Jeff Janis (@jrjanis) August 16, 2014

So forgive the 23-year-old if he got emotional one day later in front of 55,072 people at the Edward Jones Dome.

For it was his father who entered his thoughts as soon as he realized what he had just done the first time he caught the ball in a professional game on Saturday. After Janis grabbed a short crossing route from quarterback Matt Flynn in the third quarter, he flashed the speed that allowed him to run a 4.42-second 40-yard dash at the combine (only three receivers ran faster in Indianapolis this year). He turned down the left sideline and outran safety Christian Bryant to the end zone.

Then, in his words, he "kind of blacked out. It was pretty exciting."

And in an instant, it hit him.

"I think I had a pretty good guardian angel over me today," Janis said. "I'm just glad everything happened the way it did."

For Janis, it may have sealed his spot on the Packers' opening-day roster. After missing the first seven practices because of a case of shingles, which was diagnosed on the eve of training camp, Janis returned to the field with a flurry. On his first day as a full participant, he snagged a one-handed catch for a touchdown over cornerback Sam Shields. From there, not a practice went by that Janis didn't make an eye-catching play.

But he still needed to do it in a game.

Coach Mike McCarthy held out Janis from the preseason opener at Tennessee, so Saturday's game against the Rams was his first chance to show that his small-school success at Saginaw Valley State and practice-field production would translate to a game.

"It was great to get Jeff out there finally," McCarthy said. "It was great experience for him, and he continues to do something every day. That's something that you look for.”

The next step will be to do it with the starters and against an opponent's starters. That chance could come against the Oakland Raiders on Friday, when McCarthy likely will play quarterback Aaron Rodgers for more than just the two series he did against the Rams.

But the 6-foot-3 Janis already has captured his teammates' attention.

"He's made a few plays," Rodgers said. "He's athletic. He's fast. He ran his route, caught a ball and outran everybody today. When you're playing against the first string, you have to run crisp routes and make the plays that are there, so plays like today help him out confidence-wise for sure. He did it in practice last week. Coming back from his ailment, he did a nice job for us."

Said Jordy Nelson: "Janis obviously showed his speed tonight. I was very impressed. He got up the sideline."

Halfway through the preseason, Janis might be the leading contender for the fifth receiver spot behind Nelson, Randall Cobb, Jarrett Boykin and second-round pick Davante Adams, who had two catches for 28 yards against the Rams. Janis also got three chances as a punt returner. He had two fair catches and one return for 9 yards.

But Janis wasn't thinking about roster spots or depth charts after Saturday's game. This was a day for him and his dad.

"He's just probably got a big grin on his face, and he's just as excited as I am," Janis said.