Katie Taylor and Amanda Serrano shined in recent unanimous decision wins, and each of them solidified her spot in the ESPN women's pound-for-pound rankings.
Taylor (19-0, 6 KOs), 35, of Bray, Ireland, defended her lightweight undisputed championship with a dominating victory over Jennifer Han (18-4-1, 1KO) on Sept. 4 in Leeds, England. All three judges -- Luigi Boscarelli, Phil Edwards and Leszek Jankowiak -- had it 100-89 for Taylor.
Serrano (41-1-1, 30 KOs), 32, of Brooklyn, New York, via Puerto Rico, dominated Yamileth Mercado (18-3, 5 KOs) on Aug. 29 in Cleveland to defend her WBC and WBO featherweight world titles. Serrano gained ground on No. 2 Claressa Shields, but it wasn't enough to move up.
"Taylor and Amanda Serrano both had good performances, but what's keeping me from making them No. 1 on my list is that they must fight each other," ESPN boxing analyst and former two division champion Timothy Bradley Jr. said. "Make the fight happen and the winner will be without question my No. 1 pound-for-pound female fighter."
ESPN boxing writer Nick Parkinson agrees, saying Serrano's two victories in 2021 so far make a strong case for her to be ranked higher.
"Serrano probably needs to beat Taylor, or she needs Taylor to lose, to take the No. 1 spot on my list," Parkinson said. "Shields has a truck full of world title belts at junior middleweight and middleweight, while Taylor holds all four world lightweight titles. Serrano, who holds two of the major featherweight titles, is simply outnumbered by belts and recent big wins in comparison to Shields and Taylor, who have both held the No. 1 spot in 2021. Taylor has beaten tough opponents like Natasha Jonas and Delfine Persoon in the last year or so, helping her to secure that top spot.
"But Serrano is building momentum, making a proposed fight with Taylor in 2021 a difficult one to call and one that will stop all arguments as to who is the best women's pound-for-pound fighter."
ESPN's Kel Dansby decided to keep Shields as his No. 1 fighter, noting her dominance in all her pro fights.
"Shields maintains her spot atop my list. A foray into MMA has kept Shields from being as active as Taylor and Serrano, but her accolades remain unmatched," Dansby said. "Shields remains the only two-division undisputed champion of the four-belt era, man or woman, and she's dominated three divisions since turning pro. While Katie Taylor has been pushed to the brink several times while defending her undisputed title, Shields has barely lost rounds in her title fights."
Who else made the top 10? Here's the list:
Note: Results are through Sept. 7.
1. KATIE TAYLOR 
Previous ranking: No. 1
RECORD: 19-0, 6 KOs
DIVISION: Lightweight (undisputed champion)
LAST FIGHT: W (UD10) Jennifer Han, Sept. 4
NEXT FIGHT: TBA
2. CLARESSA SHIELDS Previous ranking: No. 2
RECORD: 11-0, 2 KOs
DIVISION: Junior middleweight and middleweight undisputed champion
LAST FIGHT: W (UD10) Marie Eve Dicaire, March 5
NEXT FIGHT: Dec. 11 vs. TBA
3. AMANDA SERRANO Previous ranking: No. 3
RECORD: 41-1-1, 30 KOs
DIVISION: Featherweight unified titlist
LAST FIGHT: W (UD10) Yamileth Mercado, Aug. 29
NEXT FIGHT: Dec. 18 vs. Miriam Gutierrez
4. JESSICA MCCASKILL Previous ranking: No. 4
RECORD: 10-2, 3 KOs
DIVISION: Welterweight undisputed champion
LAST FIGHT: W (UD10) Cecilia Braekhus, March 13
NEXT FIGHT: TBA
5. MIKAELA MAYER Previous ranking: No. 5
RECORD: 16-0, 5 KOs
DIVISION: Junior lightweight titlist
LAST FIGHT: W (UD10) Maiva Hamadouche, Nov. 5
NEXT FIGHT: TBA
6. DELFINE PERSOON Previous ranking: No. 6
RECORD: 45-3, 18 KOs
DIVISION: Lightweight
LAST FIGHT: W (TKO4) Beatriz Aguilar, Nov. 1
NEXT FIGHT: TBA
7. CHRISTINA HAMMER Previous ranking: No. 7
RECORD: 26-1, 12 KOs
DIVISION: Middleweight
LAST FIGHT: W (KO7) Sanna Turunen, Dec. 20
NEXT FIGHT: TBA
8. CECILIA BRAEKHUS Previous ranking: No. 8
RECORD: 36-2, 9 KOs
DIVISION: Welterweight
LAST FIGHT: L (UD10) Jessica McCaskill, March 13
NEXT FIGHT: TBA
9. TERRI HARPER 
Previous ranking: 8
RECORD: 11-0-1, 6 KOs
DIVISION: Junior lightweight titlist
LAST FIGHT: W (TKO9) Katharina Thanderz, Nov. 14
NEXT FIGHT: Nov. 13 vs. Alycia Baumgardner
10. SENIESA ESTRADA Previous ranking: 10
RECORD: 21-0, 8 KOs
DIVISION: Junior flyweights titlist
LAST FIGHT: W (UD10) Tenkai Tsunami, July 9
NEXT FIGHT: TBA
The formula
The rankings are based on a descending points system, with a first-place vote receiving 10 points, a second-place vote receiving nine points and so on.
Others receiving votes: Savannah Marshall (8), Layla McCarter (5), Hyun Choi (5), Yamileth Mercado (1), Chantelle Cameron (1), Yesica Bopp (1).
How our experts voted
Timothy Bradley Jr.: 1. Shields, 2. Taylor, 3. Serrano, 4. McCaskill, 5. Hammer, 6. Mayer, 7. Harper, 8. Estrada, 9. Braekhus, 10. Persoon
Nick Parkinson: 1. Taylor, 2. Serrano, 3. Shields, 4. McCaskill, 5. Braekhus, 6. Persson, 7. Hammer, 8. Mayer, 9. Estrada, 10. Cameron
Michael Rothstein: 1. Taylor, 2. Shields, 3. Serrano, 4. McCaskill, 5. Persoon, 6. Mayer, 7. Hammer, 8. Harper, 9. Braekhus, 10. Estrada
Michelle Joy Phelps: 1. Taylor, 2. Shields, 3. Serrano, 4. McCaskill, 5. Mayer, 6. Braekhus, 7. Harper, 8. Marshall, 9. Estrada, 10. Persoon
Salvador Rodriguez: 1. Taylor, 2. Shields, 3. Serrano, 4. McCaskill, 5. Persoon, 6. Mayer, 7. Estrada, 8. Harper, 9. Braekhus, 10. Marshall
Bernardo Pilatti: 1. Taylor, 2. Serrano, 3. Shields, 4. McCaskill, 5. Hammer, 6. McCarter, 7. Persoon, 8. Mayer, 9. Estrada, 10. Mercado
Charlie Moynihan: 1. Taylor, 2. Serrano, 3. Shields, 4. McCaskill, 5. Hammer, 6. Choi, 7. Mayer, 8. Persoon, 9. Braekhus, 10. Bopp
Kel Dansby: 1. Shields, 2. Taylor, 3. Serrano, 4. McCaskill, 5. Persoon, 6. Mayer, 7. Marshall, 8. Harper, 9. Estrada, 10. Hammer
ESPN experts' poll
First place: Taylor (6), Shields (2)
Second place: Shields (4), Taylor (2), Serrano (2)
Third place: Serrano (6), Shields (2)
Fourth place: McCaskill (8)
Fifth place: Hammer (3), Mayer (2), Persoon (2), Braekhus (1)
Sixth place: Mayer (3), Persoon (2), Braekhus (1), McCarter (1), Choi (1)
Seventh place: Hammer (2), Harper (2), Mayer (1), Persoon (1), Estrada (1), Marshall (1)
Eighth place: Harper (3), Mayer (2), Persoon (1), Estrada (1), Marshall (1)
Ninth place: Braekhus (4), Estrada (4)
10th place: Persoon (2), Hammer (1), Estrada (1), Mercado (1), Marshall (1), Cameron (1), Bopp (1)