McGlinchey's maturity and professionalism are so apparent to teammates that in the span of a roughly 15-second answer from cornerback Richard Sherman, the rookie offensive tackle aged about seven years.
"He came in here at 35 and I don't know how they messed up his birth certificate," Sherman said. "He came in here with his shirt tucked in and you thought he was somebody's dad, at least I did. He's come in and been a consummate professional. He's probably one of the better rookies that I've seen.
"He doesn't talk a lot, he comes in here, he takes care of his body, he says the right things, he does the right things, you're like 'Who coached him up?' He looks like he's 42."
The good news for the 49ers is that McGlinchey is just 23 and will put the finishing touches on a strong first NFL season at right tackle on Sunday against the Los Angeles Rams. While McGlinchey has had the usual ups and downs you'd expect from a rookie, the good has far outweighed the bad. A pick that was once questioned as a luxury selection now looks like it will deliver the Niners a piece on the offensive line they can build around for the foreseeable future.
Through 16 weeks, McGlinchey has been everything the 49ers expected as a run blocker and has improved each week in pass protection. Pro Football Focus rates McGlinchey as the NFL's best rookie offensive lineman, even outpacing Indianapolis Colts guard Quenton Nelson, his former Notre Dame teammate and 2018 Pro Bowler. A good chunk of that rating comes as a result of McGlinchey's work in the run game, where he's been an ideal fit in coach Kyle Shanahan's outside zone-heavy scheme. PFF ranks McGlinchey second among all tackles in run blocking, but just 77th in pass protection.
The Niners traded Trent Brown to New England after drafting McGlinchey at No. 9 overall. Brown was a good pass protector but didn't have the same impact on the ground attack. The 49ers believed that McGlinchey's athleticism would allow him to develop in pass protection and one day replace Joe Staley on the left side.
“McGlinchey has been great all year," Shanahan said. "Just the pressure that was put on him in the first day to come in, replace Trent and take over that spot. He showed it wasn't too big for him the first day of OTAs and he's continued throughout the year. He definitely has plays that aren't perfect, like all O-Linemen do. He's always up for the challenge of whoever he's going against. He's very prepared. If he gets beat by somebody, he doesn't panic and overcompensate. He thinks of why he did and he usually gets better as he struggles in a game. So, that's what a true O-Lineman is like and the type that usually, as long as they stay healthy, they get better as their career goes.”
As was expected, the pass protection side of things has been a work in progress. According to ESPN and NFL Next Gen Stat's new Pass Block Win Rate metric (it's a "win" if a blocker is able to maintain his block for 2.5 seconds or longer), McGlinchey has a 79 percent win rate on 483 pass sets, which ranks 19th among qualified right tackles.
McGlinchey also didn't have the benefit of being eased into the job. In fact, he's faced a veritable murderers' row of pass-rushers that includes Minnesota's Danielle Hunter, Kansas City's Justin Houston, the Chargers' Melvin Ingram, Seattle's Frank Clark (twice), Denver's Von Miller and Chicago's Khalil Mack. Against the Rams, he even got a few doses of Aaron Donald and he spent part of a week in the preseason matchup up with J.J. Watt.
Those first few weeks left McGlinchey's head swimming.
"It was just a mindset that you had to change," McGlinchey said. "I remember the first couple weeks of the season, especially the first two away games we were in Minnesota and then Arrowhead, and I was stressing about the damn crowd noise and then 'There's Justin Houston, there's Danniele Hunter, there's this, that and the other thing,' and all it did was cripple me as a player."
By the Week 4 meeting against the Chargers, McGlinchey was so in his own head that almost any time a pass play was called, he was worried about every little thing: getting on the snap on time, what move the defender might use, the crowd noise and more.
"You can feel stuff behind your eyes start giving pressure to your face," McGlinchey said. "It's just one of those things you feel overwhelmed and you feel it growing inside of you and you have to control it."
On the Niners' second offensive snap of Week 4, Ingram used a quick rip move to the inside to disengage from McGlinchey and get pressure on quarterback C.J. Beathard, who threw incomplete as Ingram closed in. The play didn't even lead to a sack but it was also the moment McGlinchey realized he needed to cut it loose.
"It was 'Well, he beat me, nothing bad happened and life is still going to go on,'" McGlinchey said. "So the mindset is you are going to lose, other guys are getting paid to play too and it's just a matter of see you again in 30 seconds when we do it again."
Credit for McGlinchey's professional approach to the NFL's daily grind can be divvied up in many places, but there were two people in particular who have helped him along the way. McGlinchey points to former Notre Dame offensive line coach Harry Hiestand, who now holds the same job with the Bears, as the person who ingrained in him the importance of having the same approach every day.
Since arriving in the pros, McGlinchey has been able to see and model his approach after the metronomic Staley. At 34, Staley remains one of the league's best tackles and is known for his ability to balance when it's time to be serious and when it's time to have fun.
Even when McGlinchey was struggling early in the season, Staley recognized that it was just a matter of having the "A-ha" moment that he once did. For Staley, it was a rough game against Michael Strahan that left him calling his dad to tell him how difficult the NFL is.
"I think once he had that realization for himself, that's the way he has to approach the NFL game, his game has improved all season long," Staley said.
While there have still been hiccups, including last week's game against Mack which Shanahan said "wasn't one of his better games," McGlinchey has showed steady progress over the course of the season. After the Week 4 struggles against Ingram, McGlinchey had two his four best pass-blocking games in Weeks 5 and 6 and has posted eight games at 75 percent win rate or above.
This offseason, McGlinchey wants to focus on getting stronger physically and mentally. He plans to look at his performances this season with an eye toward building more confidence, knowing he can hold his own against some of the game's top edge rushers.
"I think I'm not where I want to be," McGlinchey said. "I don't know if you ever are as a football player. But what I am proud of this season is that I've been stacking games together and since a certain point of midway through the season, I can feel myself getting better each and every week."