To craft a championship winning fantasy baseball roster, how you approach the waiver wire will be key. In Week 5 of the fantasy baseball season, a few players have proven worthy of a pickup.

By now, the core of many rosters will be filled. The studs selected on draft day still likely play a big role – assuming they're healthy. But every team in the league has star. It's the maximization of your roster that sets a fantasy baseball owner apart.

Finding a stud off of the waiver wire can change a whole season. They're a player everyone looked past at the draft and can now provide major benefits for free. Perhaps it's a player given an opportunity or thriving in an opportunity that wasn't expected. Adding a player in the midst of a hot streak is fantasy baseball gold.

Week 5 gives players another opportunity to find that diamond in the rough. These are our top four fantasy baseball waiver wire pickups for Week 5.

Jonah Heim – C Texas Rangers 

Jonah Heim earned a major opportunity at catcher for the Rangers last season, appearing in 127 games. Heim has been given a similar role in 2023 and hasn't looked back since.

Heim has appeared in 15 games thus far this season, hitting .320 with four home runs and 16 RBI. He has taken over as the Rangers' primary starter at backstop. His leash in that role got a bit longer after manager Bruce Bochy said it would take four weeks for fellow catcher Mitch Garver to recover from his knee injury.

With Garver out, Heim should only see more playing time. While he struggled to a .227 batting average in 2022, Heim has already gotten off to a fast start in 2023. After hitting 16 home runs and 48 RBI last year, he'll have a chance to surpass those numbers with a big season.

The Rangers have been one of the better teams in the MLB with their 13-7 record. Heim gets a boost not only from his improved bat skills, but just consistently being in the middle of Texas' lineup.

Rodolfo Castro – INF Pittsburgh Pirates

When the Pittsburgh Pirates opened their season, many tuned in to see future star Oneil Cruz. However, Rodolfo Castro has taken most of the shine in Pittsburgh recently.

Cruz fractured his left ankle, sidelining him for at least four months. In his place, Castro has taken over at short. The Pirates have been impressed with Castro's work thus far, as he has started 10 of the 12 games since Cruz has been out.

Overall, Castro has appeared in 21 games for the Pirates this season with 16 starts overall. He is hitting .273 with two home runs and eight RBI. Castro carries an impressive .385 on base percentage and .821 OPS.

In fantasy baseball, sometimes the biggest precursor to a breakout is simple opportunity. With Cruz down, Castro has been given an everyday role in the Pirates' infield. As long as he maintains that role, he will be a sneaky waiver wire addition.

Jose Alvarado – RP Philadelphia Phillies 

When the Philadelphia Phillies signed Craig Kimbrel this offseason, many expected him to be the team's closer. Instead it appears that Jose Alvarado has taken over the role.

Alvarado has converted the Phillies' last three save opportunities. Kimbrel has struggled thus far this season with a bloated 5.00 ERA.

Alvarado, in turn, has a measly 0.96 ERA over his nine appearances alongside a sterling 18/0 K/BB ratio. Not only is Alvarado earning save chances and converting them, but he's been mowing down batters in the process.

Closers are often second thoughts in fantasy baseball. But a dynamite closer can help swing any matchup. Alvarado seems to have locked up the closer role on what should be a potent Phillies team. If he keeps getting save opportunities and racking up strike outs, Alvarado is a Week 5 waiver wire pick up that could still be paying off by the championship.

JD Davis – 3B San Francisco Giants

With the roller coaster of an offseason the San Francisco Giants went on this offseason, JD Davis got lost in the shuffle. But his recent play shows that Davis shouldn't be forgotten.

Davis has made 12 straight starts for the Giants before getting the day off on Saturday. When he is in the lineup, Davis is often times batting fourth. It isn't usual to be able to land a clean up hitter off the waiver wire.

It's even more unlikely when the waiver wire pick up is hitting at Davis' clip. Over 18 total games this season, Davis is hitting .306 with four home runs and 13 RBI.

He isn't Aaron Judge, but Davis is still hitting at an impressive level. As long as he is getting starts in the middle of the Giants' lineup, Davis will be a valuable asset in fantasy baseball.