BOSTON -- A few things we learned (again) Sunday about Boston Red Sox star right fielder Markus Lynn "Mookie" Betts:

• His idea of a slump -- or at least feeling like he's "off" at the plate -- is missing one game because of tightness in his right calf, a byproduct of having fluid drained from his right knee two weeks earlier, then going 1-for-8 with one strikeout, no walks and no extra-base hits in back-to-back games.

• The way he prefers to emerge from such a condition is to report to the ballpark early before a day game that precedes a four-city, 11-game road trip, grab a bat and stay in the batting cage until he feels like he has "swung my way out of it."

• After his second three-homer game of the season in a 16-2 throttling of the lowly Arizona Diamondbacks, Betts should be considered the frontrunner for the American League MVP award.

OK, so that third point is subjective. Toronto Blue Jays third baseman Josh Donaldson is having another outstanding season, batting .292 with 26 doubles, 28 homers and a .966 OPS. Manny Machado moved from third base to shortstop and is now back at third base for the Baltimore Orioles and batting .305 with 34 doubles, 26 homers and a .915 OPS. Houston Astros second baseman Jose Altuve is again leading the league in hitting (.362) and has a career-high 19 homers. And out in Southern California, Mike Trout is doing Mike Trout-like things (.311, 26 doubles, 22 homers, 19 steals, .973 OPS) for the dreadful Los Angeles Angels.

But Betts does it all for a Red Sox team that is in the midst of a three-team fight for the AL East crown despite subpar pitching that continually threatens to drag it down. It doesn't matter whether manager John Farrell bats him leadoff, as he did for most of the season, or drops him last week into the run-producing No. 3 spot in the order in front of David Ortiz, the 23-year-old is as dynamic as any player in the majors.

Among the AL leaders, Betts ranks second in hits (154), tied for second in doubles (34), third in runs (91), fourth in slugging (.561) and WAR (6.1), tied for fourth in triples (5), tied for fifth in RBIs (84) and steals (18), eighth in OPS (.914) and tied for ninth in home runs (26). He also leads the league in at-bats (492) and has played all but 48 innings this season.

"When he gets going," Red Sox pitcher Rick Porcello said Sunday after improving to 16-3, 12-0 at Fenway Park, "it's pretty incredible what he's capable of doing."

Said second baseman Dustin Pedroia, who notched his fifth career five-hit game, more than any player in franchise history: "He's been great all year. He's a great player. There's nothing on the field he can't do. He can take over a game in a lot of ways."

Sunday was proof of that. In his previous three-homer binge, May 31 in Baltimore, Betts went deep to left field, center field and right field at Camden Yards. On Sunday, he simply took aim at the Green Monster in left field at Fenway against Diamondbacks ace Zack Greinke.

In the first inning, Betts cleared the wall, the Monster seats, the billboards and everything else with a shot that was measured at 423 feet by ESPN Home Run Tracker. He homered into the first row of the Green Monster seats in the second inning against Greinke, then clocked a 356-foot shot that hooked inside the foul pole atop the Monster and was estimated at 382 feet.

In between the homers, Betts singled and scored in the fourth inning. And when he came to the plate in the sixth inning, the crowd was chanting "Let's Go Mookie." Even his teammates were imploring him to swing as hard as he could in pursuit of homer No. 4.

But Betts hadn't spent all that time in the batting cage before the game trying to regain his swing only to mess it up again by intentionally trying to go deep.

"If it was going to happen, it was going to happen," Betts said. "I was just trying to get another hit and try to make it a five-hit day like Pedey."

There would be neither a fifth hit nor a fourth homer. Betts lined out to right field in the sixth and grounded to third to end the eighth. And as the Red Sox packed for their flight to Cleveland and a makeup game Monday afternoon, Betts incredibly described himself as "still a work in progress" at the plate.

Every hitter should have such problems.

The Red Sox would prefer not to think about where they would be without Betts, which is why they held their breath last week when he had to leave Wednesday night's game against the Yankees with discomfort in his calf. Farrell gave him a full day off to get treatment, and it's possible he might need a few more, especially with an unforgiving schedule that puts the Red Sox on the road for 30 of the season's final 46 games and doesn't afford them another day off until Sept. 1.

By then, Betts might be on the doorstep of 30 homers. Having already rubbed elbows with Ted Williams as the only Red Sox hitters ever with two three-homer games in a single season, Betts could join Williams, Tony Conigliaro and Nomar Garciaparra as the only players in franchise history to hit 30 homers before their age-24 season.

Betts could also surpass Ortiz for the team home-run lead. Having tied him at 26, he's contemplating a friendly wager with Big Papi.

"I may make a bet with him now," Betts said. "If I see it go over the fence a couple more times, I may make a bet with him."

Another day like Sunday and it will be a season for the ages for Betts, whose value to the Red Sox and around the league only continues to rise.