BOSTON -- Leading up to the start of Spring Training, the Around the Horn series is examining each of the Red Sox's positional groupings heading into the 2019 season. Our latest installment examines the middle infield.
The Red Sox's double-play combo is the most familiar grouping on the team. Shortstop Xander Bogaerts and second baseman Dustin Pedroia have been teammates for the past six seasons, though an injury to the latter kept them apart for nearly all of 2018.
• Around the Horn:Catcher | Corner infield
Entering this season, it is fair to wonder if this will be the final chapter for the Bogaerts-Pedroia duo that has provided so many highlights over the years on both sides of the ball. Pedroia and Bogaerts are both entering a crossroads for different reasons.
For Pedroia, the issue is health. His surgically repaired left knee didn't respond in 2018. Though Pedroia is optimistic he will make it back this year, there are no guarantees until it actually happens.
With Bogaerts, the issue is his contract. Coming off his most productive season, Bogaerts is eligible for free agency at the end of the season.
"I enjoy playing here," said Bogaerts. "Obviously it's a winning city, it's a winning team. We've been to the playoffs three years in a row. I don't see what's not to like about it. The contract stuff, I pretty much leave it to my agent. If we can figure something out, there's always room to talk, but I enjoy it. It's an awesome city and winning is the main priority here."

Here is a closer look at how the Red Sox are looking in the middle of the infield.
X marks the spot -- but for how long?
For all the talk about American League MVP Award winner Mookie Betts and star masher J.D. Martinez, the Red Sox had a third star in their lineup last season; Bogaerts was a force who played a major role in his team's run to a World Series championship.
Hours after being named manager of the Red Sox, Alex Cora said that Bogaerts was one of the players he expected would improve the most. Cora demanded excellence from his shortstop, and he got it.
The right-handed hitter produced career highs in doubles (45), homers (23), RBIs (103) and OPS (.883). Hitting mainly fourth or fifth, Bogaerts provided strong protection for Martinez.

Though Bogaerts will never be Ozzie Smith on defense, he is an above-average fielder who is particularly adept at making the jump throw from the hole. Bogaerts makes nearly all the plays he should, and he throws in some gems for good measure. The combination of offense and defense Boston gets from Bogaerts makes shortstop an obvious area of strength. Expect the Red Sox to make a strong push to keep Bogaerts beyond 2019.
It will be interesting to see if Boston can make any progress toward an extension in Spring Training. Bogaerts would be hard to replace via trade or free agency.

"Going into this year, you never know what can happen," Bogaerts said. "The season hasn't started yet. You never know if there's room to talk and figure out some stuff. I'm still a Red Sox for one more year."
On the comeback trail
The 2018 season was such a frustratingly short one for Pedroia that he has set himself up nicely to be the second straight Boston player to win the AL Comeback Player of the Year Award. David Price took home that honor last season. Pedroia, the team's longest-tenured player, played in only three games. Fortunately the Red Sox never missed a beat, winning it all.
Though Pedroia could probably be a fine coach at some point, he is not ready for that just yet. More than anything, the 35-year-old wants to contribute on the field again. Pedroia recently started a running program, and early indications were positive. But nobody will know what type of shape Pedroia's knee is in until he gets back into a game routine in Spring Training. He's hopeful he will be on the same schedule as the other players during camp. Even still, expect Cora to handle his second baseman conservatively while keeping the long haul in mind.

The Red Sox essentially haven't had the Pedroia they know since 2016. In '17, his left knee was never the same after Manny Machado spiked him in April. Amazingly, Pedroia still hit .293 that year, though he didn't have power due to the lack of strength in his left knee. With Pedroia under contract through '21, both sides are obviously hopeful that he can make it back.
If 2019 becomes another lost season for Pedroia, president of baseball operations Dave Dombrowki might have to explore an external option like last year, when he acquired Ian Kinsler in late July. Kinsler signed with the Padres as a free agent in December.
Who is on backup?
The Red Sox are lucky to have two of the best veteran utility players in the game in Eduardo Núñez and Brock Holt. And they can both play second and short.
At this point, Holt is probably the preferred choice to back up at both middle spots because he has more range than Nunez. For whatever reason, Nunez is more comfortable at short than second.

Nunez and Holt are both offensive threats. Expect Nunez to be better at the plate than he was a year ago, when he was dealing with discomfort and weakness in his right knee. When he is right, he has pop in his bat. Holt is known for being a contact hitter, but he belted five homers in his final 75 at-bats of the regular season.
Anyone on the farm?
Shortstop C.J. Chatham, a second-round pick from 2016, is the team's most highly touted middle-infield prospect. But he's never played above Class A Advanced, which means he's probably at least a year from making his MLB debut. Chatham, ranked No. 8 among Red Sox prospects by MLB Pipeline, is known for his strong instincts on defense and for having a habit of hitting line drives on offense.

As far as short-term solutions, the Red Sox still have Tzu-Wei Lin, who does all the little things well and has held his own in numerous callups. Lin plays second, short, third and center field.
Could this be the year Marco Hernandez re-emerges? A separated left shoulder ruined his last two seasons. For the second straight spring, he is recovering from surgery. At this time last year, the Red Sox thought Hernandez might be able to compete for the starting second-base job. At this point, it might be a stretch to expect too much from him. Hernandez can play all over the infield.