Heading into the postseason, Joe Kelly's effectiveness was considered one of the biggest questions on the Red Sox's roster.
Now, as the Sox celebrate their World Series championship, one of the biggest questions is whether they will bring the hard-throwing reliever back -- or how they'll replace him if he departs as a free agent.
Kelly posted a 4.39 ERA during the regular season, though his 3.57 FIP suggests he pitched better than his numbers indicated. He struck out 68 batters in 65 2/3 innings, and his 9.3 strikeouts per nine innings marked the second-highest rate of his career.
On the downside, Kelly issued 32 walks, giving him a 2.13 strikeout-to-walk ratio and 4.4 walks per nine innings.
By comparison, some of the other free-agent relievers were far better in that K/BB category during the regular season, including Jesse Chavez (5.41), Joakim Soria (4.69), Sergio Romo (3.75) and Player Page for David Robertson (3.50).

Once the postseason began, Kelly's strikeout rate rose to 15 per nine innings (albeit in a much smaller sample size) but the walks -- or lack thereof -- stood out above anything else. Kelly fanned 13 without walking a batter in 11 1/3 innings, allowing only two runs (one earned) for a 0.79 ERA in nine appearances.
Will Kelly's monster postseason cause executives around the league to view him differently than they might have a month ago?
"It sometimes helps in the immediate," one American League general manager said. "But just like anything, the emotion starts to wear off and people start to focus more on what they can expect, not on what he did."
The relief market is loaded again this offseason, with a plethora of options, including Craig Kimbrel, Andrew Miller, Jeurys Familia, Adam Ottavino, Kelvin Herrera, Robertson, Soria, Brad Brach, Cody Allen, Bud Norris, Romo and Chavez. There will be plenty of competition for relief arms looking for a payday.

There aren't many good comparisons for this scenario, in which an inconsistent reliever breaks out during the postseason in his free-agent year and cashes in with a larger-than-expected deal.
Brandon Morrow had a 1.46 ERA through his first 11 postseason appearances a year ago, and although he allowed four runs in Game 5 of the World Series to bloat that ERA, he pitched in all seven games of that series against the Astros, boosting his free-agent value as he landed a two-year deal worth a guaranteed $21 million to become the Cubs' closer.
But unlike Kelly, Morrow had established something of a track record in the bullpen after transitioning from a starting role, pitching to a 1.96 ERA in 63 appearances with the Padres and Dodgers in 2016-17.
Kelly has always had tantalizing stuff, though his performance on the mound hasn't necessarily matched up. As he converted from a starter into a reliever, Kelly has evolved from a sinker-reliant pitcher (he threw the two-seamer more than 65 percent of the time in 2012-13, starting 31 of his 61 outings) into a "Here it is, try to hit it" guy who challenges hitters with his impressive four-seam fastball, which averaged 98.1 mph in '18.
The right-hander used his four-seamer 49.9 percent of the time this season, keeping hitters off-balance with his curveball (18.6 percent), slider (14.9 percent), changeup (11.1 percent) and sinker (5.5 percent), the last of which averaged 97.6 mph.

"I think in this day and age, the performance in the postseason won't provide as big a bump as it might have in the past, unless there is data/information that shows a sustainable change to his stuff or how he was using it," one Major League scout said.
A look at that data shows a noticeable change in Kelly's pitch selection during those nine postseason outings. Kelly threw his four-seamer 57.1 percent of the time and his curveball 32.9 percent, those two pitches accounting for 90 percent of his total work. His use of the changeup fell to 7.6 percent and he used his sinker just 1.8 percent of the time, but the most interesting change was that he didn't throw a single slider during the postseason.
Kelly's stellar postseason could prompt teams to dream about the 30-year-old finally fulfilling the promise his powerful arm has always offered, but executives are likely to be wary when it comes to paying too much mind to those 11 1/3 innings as compared to the 625 1/3 regular-season frames he's thrown since breaking into the Majors with the Cardinals in 2012.
"I could see it increasing his value because he has stuff," another AL GM said. "There's always the hope that it's suddenly clicking at a higher level."
"A good postseason always helps," a National League GM said. "But I'm not sure it will change much."