Red Sox's Complete Guide, Preview for 2nd Half of 2021 MLB Season

A year after finishing in the American League East cellar, the Boston Red Sox have climbed to the top of the division standings once again with a 55-36 record at the All-Star break.

The offense has been among the most potent in baseball behind stellar seasons from Rafael Devers, Xander Bogaerts and J.D. Martinez. The bullpen has been vastly improved, improving from 27th in the majors in ERA (5.79) to eighth (3.57 ERA) behind lights out closer Matt Barnes.

The starting rotation has stayed healthy enough that five pitchers have made all but two starts on the year, but beyond All-Star Nathan Eovaldi, their starters have been inconsistent for much of the year.

With the Tampa Bay Rays, New York Yankees and Toronto Blue Jays all nipping at their heels as potential playoff contenders, the Red Sox will have their work cut out over the season's final months.

Ahead we've provided a preview for the second half of the season, complete with potential X-factors, a trade deadline outlook and a blueprint for this Red Sox team to reach the postseason.

LHP Chris Sale

There may be no bigger second-half X-factor than left-hander Chris Sale, who is on the mend from Tommy John surgery and poised to rejoin a Boston rotation ready to welcome him back with open arms.

The seven-time All-Star is scheduled to begin a rehab assignment on Thursday. He is expected to pitch two innings for the team's rookie league affiliate.

"If Sale adds an inning each time and everything goes smoothly, it's conceivable he could only need four rehab starts (about 20 days) before he's ready to return to the big leagues, putting a potential return in early August," wrote Jason Mastrodonato of the Boston Herald.

RHP Tanner Houck

Rookie right-hander Tanner Houck will also provide some internal reinforcement, provided he does not suffer any setbacks in his return from a flexor strain. The 25-year-old is building up his arm strength at Triple-A Worcester, with five starts of four or fewer innings under his belt since he returned to action on June 17.

In 27.1 innings of work at the MLB level over the past two seasons, he has a 1.98 ERA, 1.10 WHIP and a 33-to-10 strikeout-to-walk ratio.

CF Jarren Duran

One of the top prospects in the Boston system, Duran is raking in Triple-A this season with a .270/.365/.561 line that includes 15 home runs, 32 RBI and 12 steals in 46 games. He played for Team USA in the qualifying tournament earlier this year but is not on the team for the Olympics, so he'll be available for a promotion whenever the Red Sox see fit.

The 24-year-old could see time at all three outfield positions, or he could be inserted as the starting center fielder with Enrique Hernandez shifting primarily to second base.

Even with Chris Sale on his way back, adding another veteran starter to the mix looks like a must if the Red Sox are going to be viewed as legitimate title contenders.

Texas Rangers ace Kyle Gibson should be at the top of their shopping list.

The 33-year-old has a 2.29 ERA, 1.07 WHIP and 88 strikeouts in 102 innings this season, and he's more than just a two-month rental with a team-friendly $7.7 million contract for 2022.

A potential playoff rotation of Sale, Gibson, Nathan Eovaldi and whoever is throwing it best between Martin Perez, Nick Pivetta and Eduardo Rodriguez is far more appealing than relying on two of the guys from that final group to make starts.

The Red Sox value defensive versatility as much as any team in baseball, and with Marwin Gonzalez, Michael Chavis and Danny Santana all putting up subpar numbers offensively, someone like Pittsburgh Pirates standout Adam Frazier could also be an appealing target as the team's starting second baseman or in a super-utility role.

If they are not confident Bobby Dalbec is going to improve on the 79 OPS+ he posted during the first half, veteran first basemen such as C.J. Cron could also be of interest with the Colorado Rockies poised to move short-term assets.

The Red Sox are not going to coast to an AL East title, even if the rival New York Yankees are unable to right the ship during the second half.

The Tampa Bay Rays are an unorthodox contender that is lacking in star power with a seemingly cobbled together pitching staff, but that's how they operate, and they've been extremely successful doing it. With just a 1.5-game cushion over the Rays in the standings, the two teams could be considered co-favorites at this point to walk away with a division title.

A fast-rising Toronto Blue Jays team also can't be counted out of the race, especially if they add a couple of quality arms at the trade deadline.

If the Red Sox are going to hang on and win the division, the starting rotation is going to be the X-factor.

The team has to be careful not to view Chris Sale as a savior, and anything he contributes coming off a long layoff should be viewed as a bonus rather than a necessity. That means targeting another arm for the rotation at the trade deadline, and perhaps adding more length to the bullpen.

They're going to score plenty of runs. It's up to the pitching staff to hold up its end of the bargain.

All stats courtesy of Baseball Reference.