The Oakland Athletics have the best record in baseball at 66-41, the largest run differential at plus-162 and, at 3.32, the lowest ERA among starters in the American League. On Thursday, the A's traded from a position of strength to improve their rotation, as they eye a third consecutive postseason appearance. But the postseason is not enough. It's now World Series or bust.

The A's sent outfielder Yoenis Cespedes -- fresh off his second consecutive Home Run Derby win and the most recognizable player on the team -- to the Boston Red Sox for left-handed starter Jon Lester and outfielder Johnny Gomes. The Red Sox also picked up the A's 2015 competitive balance draft pick. The teams will also exchange cash to offset the remaining salaries owed to Lester and Cespedes this season, with a net $1.15 million going to the A's. Lester and Gomes will be free agents at the end of this season. Cespedes will have the option to become a free agent after next season under his original deal with the A's.

This was a gutsy and creative move by A's general manager Billy Beane. It's not every day that a first-place team trades a middle-of-the-order power threat to strengthen a rotation. There's no doubt the move was informed by the A's recent postseason history, including consecutive losses to the Detroit Tigers in the American League Division Series. In 2012 and 2013, the ALDS went the distance with then-Tigers ace Justin Verlander shutting down the A's in Game 5 in Oakland. The A's threw everything they had at a Tigers rotation of Verlander, Max Scherzer, Anibal Sanchez and Doug Fister, and it simply wasn't enough. The A's didn't have the starters to go toe-to-toe with Detroit's.

By adding Jon Lester, the A's hoped to finally have the upper hand.

Several hours later, the Tigers acquired David Price from the Tampa Bay Rays.

Move. Counter-move.

In Lester, the A's got a 30-year-old starter having the best season of his career and a postseason veteran who won two World Series with the Red Sox. Through 143 innings pitched in 2014, Lester's struck out 25.7 percent of batters and allowed a batting average against of only .235. He's given up just nine home runs while pitching half his games in hitter-friendly Fenway Park. His 2.52 ERA is the fifth-lowest in the American League; his 2.62 FIP (field-independent pitching) is even better when compared to his peers, coming in at fourth lowest in the AL. FanGraphs calculates that Lester has been the third-most valuable pitcher in the majors this season, after the Seattle Mariners' Felix Hernandez and the Cleveland Indians' Corey Kluber.

Lester now becomes the No. 1 starter for a rotation that features Sonny Gray, Scott Kazmir, Jeff Samardzija and Jason Hammel or Jesse Chavez. At 24, Gray is in his first full season with the A's and became their Opening Day starter after Jarrod Parker was lost to Tommy John surgery. He's not the strikeout machine Lester is, but he's incredibly stingy when hitters get a bat on the ball. They're hitting only .221 off Gray with only seven home runs. In July, Gray allowed only six runs (four earned) in 35 innings pitched. Kazmir is 17 days younger than Lester, but is experiencing a breakout season after an up-and-down career that saw him pitching in an independent league in 2012. His batting average against is lower than both Lester's and Gray's at .214. When combined with a 5.9 percent walk rate, it's no wonder his 2.37 ERA is the third-lowest in the American League.

Samardzija and Hammel landed in Oakland after a splashy trade in early July with the Chicago Cubs. The A's parted with their top position player prospect (shortstop Addison Russell), a Class-A outfield prospect (Billy McKinney) and right-handed starter Dan Straily. So far, Samardzija's been a boost to the A's rotation with a 3.19 ERA/4.00 FIP over 36.2 innings, but those even those numbers pale when compared to what Samardzija's accomplished overall this season: 2.92 ERA. 3.33 FIP and .231 batting average against in 144.2 innings.

Chavez was pulled into starter duty after the spring-training injuries to Parker and AJ Griffin, and he gave the A's more than they could've hoped for. Before the All-Star break, he tossed 114.2 innings in 19 starts and yielded a 3.14 ERA, but he's faded fast in the second half. Hammel has been a big disappointment since coming over from Chicago -- a 9.53 ERA in four starts, all losses. Hammel's weak performance may very well have prompted Beane to get Lester, even if meant giving up the popular Cespedes.

The A's likely will replace Cespedes in left field with a platoon of lefty-masher Jonny Gomes and righty-masher Stephen Vogt. Gomes is back in Oakland after a successful 2012 campaign with the A's in which he hit .262/.377/.491 with 18 home runs in 99 games. Gomes grew up in Petaluma, Calif., about 40 miles north of Oakland, and was a fan favorite. This season he's hitting .302 with a .400 on-base average in 116 at-bats against left-handed pitching. Vogt is a catcher who's played mostly first base and outfield for the A's since his mid-June call-up. He's the poster boy for the A's emphasis on platoons and flexibility and doing whatever manager Bob Melvin needs you to do on any given day. Vogt's numbers against right-handers are eye-popping: .365/.396/.524 in 125 at-bats.

If Vogt and Gomes can sustain those platoon splits, they will more than make up for Cespedes' production at the plate -- .256/.303/.464 with 17 home runs -- but neither will come close to replicating Cespedes' missile-like throws from the outfield. For defensive wizardry in the outfield, the A's will turn, once again, to Sam Fuld, whom Oakland also acquired on Thursday, in a trade that sent Tommy Milone to the Minnesota Twins. Fuld was on the A's Opening Day roster but was designated for assignment two weeks into the season when Craig Gentry came off the disabled list. Gentry is back on the DL after breaking his right hand last Sunday when he was hit by a pitch attempting to bunt. Fuld is likely to see time in center field -- to spell relief for Coco Crisp, who's dealing with a degenerative nerve condition in his neck -- and as a late-inning defensive replacement for Gomes and Vogt.

The A's are in "win now" mode. Adding Lester to the rotation is a significant upgrade down the stretch as Oakland tries to fend of the Los Angeles Angels for the American League West title. And they want that title, because nobody wants their postseason hopes to rest on a one-game crapshoot for the Wild Card. Lester brings a wealth of postseason experience and success, which was in short supply for the A's the last two years. In 13 postseason games dating to 2007, Lester is 6-4 with a 2.11 ERA.

The A's gave up a popular, powerful player in Cespedes, but one who was inconsistent at the plate. Gomes and Fuld are quintessential A's-type players: guys who will gut out every at-bat, give maximum effort in the field, and keep everyone loose in the clubhouse -- a clubhouse that wants three champagne-soaked showers so badly, they can taste it.