A year ago, Bryce Harper put together one of the best offensive seasons of recent memory.

In 2016, it's been a different story, as some combination of opponents' adjustments, bad luck and his own mechanical and physical issues have conspired to drag down his numbers. After a hot start seemed to signal that Harper's dominance would continue indefinitely, he hit a pedestrian .214/.333/.351 from mid-May through Aug. 6, struggled even more since the All-Star break, then sat out five games with a stiff neck.

Harper did return in highly encouraging fashion on Sunday and Monday, going 4-for-6 with three doubles and three walks, then went 2-for-4 with a homer on Wednesday, suggesting a late-season surge is possible. But his up-and-down campaign still makes Mike Trout's consistent excellence stand out more starkly.

Harper has reached greater heights with the bat. His 195 adjusted OPS+ in 2015 is a good bit better than Trout's career-best 179 from two years earlier. It would surprise few if the Nationals star makes it back to that level. Trout, on the other hand, has achieved a degree of almost robotic precision.

Baseball is an unforgiving game, mentally and physically, but Trout has managed to keep himself on the field while making the necessary adjustments. While he might create them in slightly different ways, his numbers always seems to end up in about the same spot:

2012: 639 PA, 168 OPS+ (2nd in MLB)
2013: 716 PA, 179 OPS+ (2nd in MLB)
2014: 705 PA, 168 OPS+ (3rd in MLB)
2015: 682 PA, 176 OPS+ (2nd in MLB)
2016: 498 PA, 169 OPS+ (2nd in MLB through Wednesday)

Barring a significant slide over the last quarter of the schedule, Trout is going to join an exclusive club with this metronomic stat line. Since the dawn of the 20th century, only nine others have strung together at least five consecutive qualifying seasons with an OPS+ of 160 or better. Here is the impressive list in reverse chronological order.

  • Barry Bonds 1990-98, 2000-04
  • Frank Thomas 1991-97
  • Stan Musial 1948-54
  • Johnny Mize 1936-40
  • Lou Gehrig 1927-37
  • Babe Ruth 1918-24, '26-'34
  • Rogers Hornsby 1920-25
  • Ty Cobb 1907-19
  • Honus Wagner 1902-09

(Ted Williams likely would be on this list if not for his military service. He topped the 160 mark while qualifying for the batting title in each of his first eight seasons, which were interrupted by three seasons lost to World War II. It's also possible that others are in the same boat, including Charlie Keller, who hit the mark from 1941-43 and again in '45 after a year away).

Not only would Trout be just the third player in the past 70 years to accomplish this feat, but he also is doing it while playing a premium defensive position -- and in his age 20-24 seasons (he turned 25 on Aug. 7). Only Cobb, more than a century ago, has had five qualifying 160 OPS+ seasons at such a young age. Only Cobb and Williams can top Trout's career OPS+ of 169 up to this point (minimum 2,000 plate appearances). And of course, Trout is more than just a good hitter, as he is closing in on Cobb's record of 46.7 wins above replacement by the end of the age-24 season.

None of that should minimize what Harper has accomplished. Even at his lowest, in 2014, he was a 21-year-old who was roughly 10 percent better than league average at the plate. And at his best last year, he posted the second-best OPS+ by a player 22 or younger, behind only Williams.

The type of drop-off Harper is experiencing -- to a still-solid 120 OPS+ -- isn't completely unprecedented, either. In the past 100 years, his 2015 was the 34th season (by 23 different players age 25 or younger) to qualify for the batting title with an OPS+ of 175 or better. Seven others fell to below 150 the next year.

  • Boog Powell, 1964-65, from 176 to 112
  • John Olerud, 1993-94*, from 186 to 124
  • Reggie Jackson, 1969-70, from 189 to 127
  • Rocky Colavito, 1958-59, from 180 to 133
  • Musial, 1946-47, from 183 to 134
  • Joe Medwick, 1937-38, from 182 to 141
  • Arky Vaughan, 1935-36, from 190 to 148

*strike-shortened season

All seven of those players enjoyed stellar careers, and four were Hall of Famers, with Musial an inner-circle great. Yet even for them, there were peaks and valleys. It's almost inevitable.

Unless, perhaps, you're Mike Trout.

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Andrew Simon is a Sports on Earth contributor and a reporter for MLB.com. Follow him on Twitter @AndrewSimonMLB.