Milos Zvekic recommends NBA forwards and centers (PF, C, PF/C) as waiver wire pickups for fantasy basketball in Week 21. These centers and forwards can be fantasy sleepers.

With fantasy playoffs just around the corner, it's time to fit those last pieces into your puzzles. If that piece is a "big one", you may find this article interesting. There aren't any long term moves at this point, unless you're in a dynasty league, so we will be taking a different approach today by focusing on some recent injuries to centers and power forwards, and the impact they have on other players on their team who play the same position.

Of course, we will have to stick with our usual routine a bit too, since JaMychal Green is getting hot, so it will be a mix of the old and new.

Welcome to RotoBaller's Week 21 waiver wire pickups for power forwards and centers.

Standard League Waiver Wire Big Add

JaMychal Green, PF, MEM (23% Owned)

JaMychal Green has been pretty good this whole season. Heck, he is ranked around the top-100 in my Yahoo H2H 10-cat league which counts double-doubles as the 10th category. He is averaging 9.1 PTS with 0.7 3PM on 49.9 FG% and 80.8 FT%, 7.4 REB, 1.1 AST, 0.6 STL, 0.5 BLK and 1.3 TO in 28 minutes per outing. Now those stats aren't overwhelming, but those rebounds along with a humble contribution in all categories without being hurtful in any do deserve better than just 23% ownership, don't they?

Granted, Green had his ups and downs during the season, but he is on the rise again with averages of 13.0 points and 0.5 3-pointers on 65.6% from the field and 88.9% from the charity stripe, 8.8 boards, 0.3 blocks and 1.5 turnovers in 25 minutes a game in his last four. He didn't record any assists or steals in that period, but he did double-double twice and the percentages and boards alone deserve a look in most leagues.

JaMychal is the starter in Memphis, and he is a shoo-in to log 25-30 minutes a game the rest of the way for the struggling Grizzlies. If you like what he brings to the table be sure you don't leave him on the waiver wire for too long. Moreover, Memphis plays 11 times in the three default fantasy playoff weeks (20-22) and three of those contests come on nights with six games or less.

Standard League Honorable Mentions: Willie Cauley-Stein (46% owned), Willy Hernangomez (42% owned)

Waiver Wire Big Adds Based On Changes In Teams

Phoenix Suns - Alan Williams, PF/C (56% Owned) & Marquese Chriss, PF (26% Owned)

Both Marquese Chriss and Alan Williams are currently in a much larger role compared to the beginning of the season. In his first 24 games with the Suns, Chriss has played more than 20 minutes just five times. Williams was in an ever worse position, having played in only 14 regular season games before Jan. 17. But then it all changed.

Their competition for frontcourt minutes got swept aside by the two youngsters. Dragan Bender got injured, Tyson Chandler fell victim to Suns turning their attention toward developing their talent and Alex Len was heavily outplayed by both heroes of our story. Furthermore, Len has hurt his hip and has missed the Suns' last game against Dallas on March 11.

Chriss has been very good in his last four games with averages of 10.5 PTS with 1.5 3PM on 59.3 FG% and 66.7 FT%, 6.3 REB, 0.5 AST, 0.8 STL, 2.5 BLK and 1.0 TO in 26 minutes. That's top-50 value in standard leagues. Williams has been even better, double-doubling in six of his last eight games, racking up 13.8 points on 56.1 percent from the field and 66.7 percent from the line, 10.5 boards, 0.9 dimes, 1.1 steals, 1.4 blocks and 1.1 turnovers in 27 minutes per outing.

While it's hard to believe that the pair can keep up this kind of play the rest of the way, there's no reason to think that either of them won't remain fantasy relevant. They are both expected to see minutes in the high 20s and if they remain on roughly the same course, any fantasy team would be lucky to have them.

San Antonio Spurs - David Lee, PF/C (19% Owned) & Dewayne Dedmon, PF/C (9% Owned)

LaMarcus Aldridge is having problems with his heart. It's being called a minor heart arrhythmia, and Aldridge has been through similar issues before so it doesn't sound too serious, but it's still the heart so it should never be taken too lightly. He is out indefinitely and I'm sure that the Spurs are going to take the "health first" approach with their star. Get well soon LMA!

David Lee and Dewayne Dedmon, along with Pau Gasol, will be asked to fill his shoes.

Dedmon has already been playing around 20 minutes a game in the previous 30 days and has averaged 6.5 PTS on 72.0 FG%  and 80.0 FT%, 8.0 REB, 0.8 AST, 0.5 STL, 1.1 BLK and 1.6 TO in that period. His efficiency is off the chart, and he certainly won't be able to keep those percentages up, especially with no Aldridge to draw the defense's attention to himself. Furthermore, Dewayne is a 67.7% career free throw shooter, so that should take a slight hit as well. But if he gets a few more minutes, the rebounds and defensive stats could be enough for owners in deeper leagues in need of a big to consider him.

David Lee was already asked to take over for Pau Gasol while he was out from Jan. 19 to Feb. 25, and he stepped up! In that period Lee averaged 10.1 PTS on 61.0 FG% and 62.5 FT%, 6.9 REB, 1.9 AST, 0.6 STL,  0.6 BLK and 1.4 TO in 22 minutes a game. We can probably expect similar contributions from the veteran in the Spurs' attempt to fill the void left by Aldridge. Moreover, Lee was a beast with LaMarcus being rested on March 8, going 8-of-9 from the field and 2-of-5 from the line for 18 points, 10 boards and two blocks with two turnovers in 31 minutes against the Sacramento Kings. He's still got it! And the opportunity to show it has presented itself.

Both of these players are good rebounders with great field goal percentages, and while you shouldn't expect Lee to contribute as much as Dedmon in defensive stats, he can get hot in a hurry and stuff the opponent's basket. And if the fantasy playoff schedule is important to you, San Antonio plays 4-3-4 games in the next three weeks and three of those games come on nights with 6 or less scheduled games.

Deep League Honorable Mentions: Bobby Portis (18% owned), Trey Lyles (23% owned)