Development is rarely just upward. It fluctuates, players lose matches, but the key is, what is the overall trajectory? If it is upward, then all is good. All players stutter, but it is only when the stutter becomes a stall that we should be worried.
Take Borg vs. Laver. Borg slaughtered Laver in their first match, 6-1 6-1. Borg was 17, Laver 35. Laver must have said, "No way I roll over for this young pup" and adjusted, winning their next two matches, also in 1974. In a way they were like Federer/Sampras in 2001, one on the way down, the other on the way up. Laver, while starting to slip a bit, was still elite and finished the year #4. Borg was a very mature 17-18 year old in 1974, winning his first Slam.
Laver continued to slip (he fell to #10 in 1975 and then plummeted to #73 in 1976) and Borg stabilized as one of the top players on tour. Borg won their next (and last) four matches, two in 1975 and two in 1976.
If we dialed back to the end of 1974, we might have thought, "this kid is promising, but he can't beat the old guys." He was 1-2 vs Laver that year, 0-2 vs Newcombe, 1-2 vs Nastase. Not to mention, after beating Jimmy Connors in their first match in 1973, he lost six straight to the #1 through 1976, then won 4 of 6 in 1977-78, then 10 straight from 1979-81.
My point being, you have to look at the overall trajectory. Great players lose to lesser players. Tennis involves dozens and dozens of matches every year. No player can be fully on for everyone of 50-90 matches in a given year. I mean, only three players have won 95% of their matches in any year, Connors in 1974 (96.0%), McEnroe in 1984 (96.5%), and Federer in 2005 (95.3%) and 2006 (94.8%). Even Novak in 2015 "only" won 93.2% of his matches, and in the "Greatest Season Ever," Laver in 1969 won 87.2% of his matches.
Not to mention, let's have some moderation in our hopes about any given young player. Hurkacz could win more Masters and even be a darkhorse at a Slam. I seem him in a similar category as Berretini and Rublev, but I don't expect him to be a #1 or multi-Slam winner. Humbert and Khachanov seem in the next tier down, more like top 20 guys than elites. Sort of like Ruud and Opelka. Too soon to say about Rune, although as of now he's behind FAA, Sinner, Musetti, and Alcaraz among "Millenial Genners." Maybe he's in the next group with Kecmanovic, Popyrin, and maybe Shapovalov (who seems like a wildcard, could take another step into the elite or be more of a Raonic/Dimitrov level player).
,I know Judy Murray is a big fan of Lopez
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