The Fantasy Baseball season marches on as we are nearly halfway through the 2023 regular season. Whether you're dominating, contending, or struggling to hold on, fantasy baseball trades are a surefire way to improve your roster. With that, figuring out who is over and underachieving is the key to figuring out the top fantasy baseball buy and sell options. Thankfully, we have you covered with five Fantasy Baseball players to buy/sell ahead of Week 13.

*Stats up to date through 6/19

Week 13 Fantasy Baseball Buy Trade Targets

BUY: Pablo Lopez | MIN SP

3-3 Record | 4.27 ERA (3.16 xERA) | 1.11 WHIP | 101 Ks (10.8 K/9)

Twins starter Pablo Lopez comes in as our top buy-low trade target for Week 13. Lopez's ERA is north of 4.00 for the first time since 2019 – yet he's a top-20 SP in points leagues. While Lopez's ERA leaves a lot to be desired, he's gotten incredibly unlucky with lower expected (x) stats across the board compared to his actual numbers. Among pitchers with 150 balls in play, Lopez ranks seventh in xERA and eighth in xwOBA.

The rest of Lopez's baseball savant page is just as impressive. He sits 80th percentile in xBA and 71st in xSLG allowed. Lopez's expected stats aren't the only desirable part of his game, however, as he sits in the 84th percentile with a 29.2% strikeout rate while maintaining a stellar 6.8% walk rate. Lopez is coming off two consecutive strong outings but may not be viewed as the top-end starter he'll be the rest of the year. This could be your last chance to buy ahead of Fantasy Baseball Week 13.

SELL: Thairo Estrada | SF 2B/SS

.291 BA (.244 xBA) | 9 HR (10.7 xHR) | 28 RBI | 17 SB

Giants middle infielder Thairo Estrada ranks inside the top 15 in ESPN points leagues and fourth in ESPN's roto player rater. Estrada has solidified himself as a solid option but if you can get starting-level value for him I'd sell him in a heartbeat.

The biggest issue with Estrada is his lack of hard-hit balls. The 27-year-old sits in the third percentile league-wide in Average Exit Velocity and the 15th in Hard Hit Rate. He's striking out more (16.5% to 23.5% this year) and walking less (6.1% to 4.9% this year). Estrada will help you with stolen bases, but he's unlikely to keep up his home run pace given his lack of hard contact. When his average inevitably regresses, you're looking at a fringe steals contributor in a year steals can be found in abundance. Sell Estrada in Fantasy Baseball's Week 13 before his expected stats catch up with his actual output.

BUY: Willson Contreras | STL C

.205 BA (.242 xBA) | 8 HR (3.9 xHR) | 28 RBI | 5 SB

Willson Contreras has had an eventual first few months in St. Louis. After a strong 2022 that saw him bat .240 with 22 home runs in a bad Cubs offense, Contreras' brought high expectations into his first season with the Cardinals. Rather than output the career year many were projecting, Conteeras has been abysmal (although, the organization hasn't handled him well, either). He's lost his confidence – batting .158 in May and then .135 in June.

Despite this, Contreras is eligible as a catcher in every fantasy baseball format. Even with his struggles over the last month, he still ranks as the 11th-best catcher in points formats. His underlying numbers remain strong, however, with high expected ratios pointing to some positive regression inbound. Contreras is still hitting the ball hard – ranking in the 82nd percentile in Average Exit Velocity and the 99th in Max Exit Velocity. He's barreling the ball in the 70th percentile and resides in the 71st in Hard Hit Rate. For as bad as Contreras (and the Cardinals) have been thus far, it isn't farfetched to see them pick it up over the second half of the season. With how he's been playing thus far, you could buy a top-five catcher rest-of-season for pennies on the dollar.

SELL: Tony Gonsolin | LAD SP

4-2 Record | 2.92 ERA ( 4.57 xERA) | 1.01 WHIP | 43 Ks (7.4 K/9) 

Dodgers starter Tony Gonsolin is someone I'm looking to trade away in fantasy baseball this week. He lit the fantasy community on fire last season. He started 16-1 with a sub-2.50 ERA before missing essentially the rest of the regular season with an injury. While Gonsolin spent the first month of 2023 on the IL, he's given owners similar production since returning. He owns a stellar 2.92 ERA and 1.01 WHIP through eight starts. Given the landscape of fantasy pitching, Gonsolin should fetch a pretty penny.

But why would you want to trade him? For starters, Gonsolin is due for ERA regression even dating back to last year. He held an xERA of 3.12 last season – a number that skyrocketed to 4.37 this year. However, he's also not striking anyone out. His 19.8% K rate not only sits in the 20th percentile league-wide but marks the third consecutive season his strikeout rate has gone down. The righty's strong numbers the last two seasons and his role on the Dodgers give Gonsolin value in the bigs. However, for fantasy baseball, I'd sell him off for any of the buy names listed going into Week 13.

BUY: Dansby Swanson | CHC SS

.264 BA (.264 xBA) | 7 HR (6.8 xHR) | 30 RBI | 4 SB

Dansby Swanson is the last guy I'm looking to trade for in Fantasy Baseball for Week 13. Chicago's shortstop hasn't been bad, but he's lacking the power and speed combination that propelled him to a top-five SS finish in points leagues last year.

Hitting-wise, Swanson is going to turn things around. His baseball savant page is impressive. Swanson sits in the 86th percentile in xwOBA, the 82nd in Barrel Rate, and the 79th in Walk Rate. Among qualified shortstops, Swanson has the second-biggest difference in his actual and expected slugging percentage – which hopefully points to some positive regression in the future. The Cubs dropped him down to fifth in their lineup and he began to heat up with a .270 average and four RBI over his last nine games. The stolen bases may never come in Chicago but his power should continue to climb as the summer marches on.