BOSTON -- By day, Aaron Judge hit a home run at Yankee Stadium that looked as though it would never land. By night, the Boston Red Sox played a game at Fenway Park that felt as though it would never end.

And after the Red Sox lost 8-3 to the Detroit Tigers on Sunday, the New York Yankees had a four-game lead in the American League East, their largest advantage yet this season.

That's the reality facing the Red Sox as they wake up Monday. With 100 games still remaining on the schedule, they're 34-28, the third-best record in the league. At long last, their optimal lineup is back together. And with reliever Carson Smith closing in on a minor-league rehab assignment in his long road back from Tommy John elbow surgery and lefty Eduardo Rodriguez nearly ready to test his balky right knee by throwing off a mound, the pitching staff is finally almost healthy, too.

Yet the AL East has been all about the Yankees, whose surprisingly speedy rebuild is symbolized by Judge's majors-leading 21 homers, each seemingly more majestic than the last.

The Red Sox? They're still trying to find their identity in the post-David Ortiz era.

It has been difficult for Boston to evaluate their roster, according to president of baseball operations Dave Dombrowski, because of the many injuries that have prevented it from being whole. But now that lefty David Price, third baseman Pablo Sandoval and second baseman Dustin Pedroia, in particular, have returned from the disabled list, the picture is getting clearer.

Third base is the biggest trouble spot.

When Sandoval came back after missing a month with a knee sprain, it was expected that he would play against right-handed pitching while having to earn back his at-bats against lefties. But Sandoval -- and his .205 average and .617 OPS -- was on the bench Saturday night against Detroit Tigers righty Justin Verlander after continuing to show severely limited range in the field one night earlier.

Like most teams, the Red Sox could stand to add pitching depth. Drew Pomeranz labored through another difficult start Sunday night, throwing 93 pitches in only 4⅓ innings. Considering Price is not yet in midseason form after missing two months with an elbow injury, questions abound about Rodriguez's knee, and knuckleballer Steven Wright is out for the season after knee surgery, Dombrowski will feel some urgency to pick up another starter before the July 31 trade deadline.

But the Red Sox were built around their "Big Three" starters. And as long as ace Chris Sale, Rick Porcello and Price stay healthy, the Red Sox almost certainly will improve upon a 16-13 record in their starts. Compared to the Yankees and the AL West-leading Houston Astros, the need for starting pitching isn't nearly as pressing in Boston.

Third base is another story. The leash on Sandoval is shorter than ever, and there aren't many internal options. Deven Marrero is a slick fielder, but the Red Sox don't score runs consistently enough that they can afford to stash such a light hitter at the bottom of their batting order. Josh Rutledge isn't a long-term answer. And 20-year-old top prospect Rafael Devers is still in Double-A. As much as the Red Sox like him, they would be hard-pressed to hand him the job.

Expect, then, to hear plenty over the next six weeks about Chicago White Sox third baseman Todd Frazier, who noted recently that several of his friends are already texting him in anticipation of a possible trade to Boston. Frazier was batting .210 entering play Sunday, but he's one season removed from hitting 40 homers. And with Frazier eligible for free agency after the season, it may be hard for the White Sox to ask for an elite prospect in return.

Kansas City Royals third baseman Mike Moustakas figures to get plenty of attention on the trade market, too. Oakland Athletics infielder Jed Lowrie, who began his career with the Red Sox, will also be available before the deadline.

According to Dombrowski, most teams haven't given up on trying to win this year. Other than a handful of teams that were already focused on building for the future when the season began (the Philadelphia Phillies, for example, who visit Fenway on Monday night), Dombrowski says few clubs have identified as clear-cut sellers at this point.

But once the amateur draft is over by the middle of this week, more teams might begin to engage in trade talks ahead of July 31.

"Right now, it's more of an information-gathering time period," Dombrowski said recently. "I think it's more of a situation where you're talking to clubs, you have a pulse of what's going on -- not always necessarily me, but being in a position where some of our scouts are out there talking."

These days, everyone is talking about Judge and the Yankees. But if the Red Sox are able to land a third baseman who can hit in the middle of the order, the next 60 games could look a lot different.