FOXBOROUGH , Mass. — It was the Giants’ final practice before their final preseason game, Thursday night against the Patriots at Gillette Stadium, and C.J. Conrad flashed on Tuesday afternoon.

The 23-year old rookie tight end out of Kentucky lowered his 6-foot-4, 247-pound frame toward the turf and turned what looked like a certain incompletion into a nifty shoestring catch across the middle in traffic.

It was merely one play for a long-shot undrafted free agent, but it was everything at that very moment, because everything counts at this time of year for players like Conrad who are fighting for a spot on the final 53-man roster that must be trimmed from 90 by day’s end on Saturday.

“They’re constantly evaluating,’’ Conrad said. “I don’t think the process is over. So, until the last day, until Saturday [cutdown day], I feel like I’m constantly getting evaluated, and I take that very seriously.’’

Conrad is a serious, driven young man who’s determined not to let a terrible, fateful bad break back in February, when he was diagnosed with a heart ailment that scared teams from drafting him, derail his dream of playing in the NFL.

“I’m just trying to leave the best last impression possible,’’ Conrad said. “So, this game [against the Patriots] is big for me, and I’m excited for the opportunity, because I feel like I’m going to get a lot of time, a lot of opportunity for me to show the tight end I think I am.’’

Conrad had 80 catches for 1,015 yards and 12 touchdowns as four-year starter at Kentucky, but Giants coach Pat Shurmur has particularly praised his blocking. The Giants play a two-tight-end package in their base offense, with No. 1 tight end Evan Engram more of a receiver than a blocker. Veteran Rhett Ellison is the other starter.

Conrad, who enters Thursday’s game with four catches for 26 yards in preseason, is battling Scott Simonson, who has one receptions for 3 yards, for the third tight-end spot. It’s likely the Giants will keep four tight ends, which should give Conrad a good chance of sticking, but Shurmur, after Tuesday’s practice, didn’t show his hand at all when asked about Conrad.

“We’re pleased with the progress he’s making,’’ Shurmur said. “We’ll see, in the final analysis, if he makes it or not.’’

Conrad is a little more familiar with pressure than many young players his age. That heart scare, which ended up not being as serious as doctors initially diagnosed, threw Conrad’s life into a tailspin for a few moments. He was a projected mid-round draft pick who, because of the timing of his diagnosis, went undrafted.

NFL rosters are littered with undrafted players, but there are many more of them who end up on the street looking for day jobs.

Conrad said the heart diagnosis, discovered at the NFL Scouting Combine, “took me by surprise a lot, it blindsided me.’’

“I thought [the doctors] were wrong, because I had just felt so good and had been training so hard for the combine, All-Star games, pro day,’’ he said. “I just felt so healthy, was in the best shape of my life, and for them to tell me that, I really didn’t believe them.’’

Suddenly, Conrad went from thinking he had it all to wondering about his future.

“I was angry, and I feel like I still am a little angry in a way,’’ he said. “It was a tough time for me, because getting drafted was one of my biggest goals and dreams, and I felt like that was taken away from me.”

Conrad, though, was able to reboot and use his harrowing experience to his advantage.

“It was a hard thing to manage at the time, but going through this process has given me a lot of perspective — especially through this process, when there are a lot of nerves and anxious feelings about what the outcome is going to be [making the Giants roster],’’ he said. “Three months ago, I wasn’t even going to be in this position, so it’s given me a little bit of perspective on things and kind of calmed me down through some tough times.’’

Once Thursday night’s game is over, Conrad plans to do everything he can to take his mind off of Saturday’s cutdown day.

“I’m going to watch my brother play college football [at Ohio], I’m going to watch Kentucky play, just try to keep my mind off of it, although that’s going to be impossible,’’ Conrad said. “I’ll try to keep busy. Truthfully, I’ve never been in this position before. But right now, the focus is putting the best film together on Thursday, playing the best I can, leave it all on the field and live with the result.’’