# 2021 JSM Challenger of Champaign–Urbana – Singles

J. J. Wolf was the defending champion but lost in the semifinals to Stefan Kozlov.
Kozlov won the title after defeating Aleksandar Vukic 5–7, 6–3, 6–4 in the final.

## Seeds

* Daniel Altmaier (second round)
* Mitchell Krueger (quarterfinals)
* J. J. Wolf (semifinals)
* Aleksandar Vukic (final)
* Jason Jung (second round)
* Prajnesh Gunneswaran (first round)
* Blaž Rola (first round)
* Stefan Kozlov (champion)

## Draw
### Key

* Q = Qualifier
* WC = Wild card
* LL = Lucky loser
* Alt = Alternate
* SE = Special exempt
* PR = Protected ranking
* ITF = ITF entry
* JE = Junior exempt
* w/o = Walkover
* r = Retired
* d = Defaulted
* SR = Special ranking

### Finals

| Semifinals | Semifinals | Semifinals | Semifinals | Final | Final | Final | Final | Final |
| | Yosuke Watanuki | 6$^8$ | 4 | | | | | |
| 4 | Aleksandar Vukic | 7$^{10}$ | 6 | | | | | |
| 4 | Aleksandar Vukic | 7$^{10}$ | 6 | 4 | Aleksandar Vukic | 7 | 3 | 4 |
| | | | | 8 | Stefan Kozlov | 5 | 6 | 6 |
| 3 | J. J. Wolf | 2 | 3 | 8 | Stefan Kozlov | 5 | 6 | 6 |
| 8 | Stefan Kozlov | 6 | 6 | | | | | |

### Top half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 1 | D Altmaier | 6 | 6 | | | | | | | | | | | | | | |
| | M Jaziri | 3 | 4 | | 1 | D Altmaier | 2 | 1 | | | | | | | | | |
| | A Galarneau | 4 | 6 | 0 | | Yo Watanuki | 6 | 6 | | | | | | | | | |
| | Yo Watanuki | 6 | 4 | 6 | | | | | | | Yo Watanuki | 6 | 6 | | | | |
| | P Krstin | 7 | 7 | | | | | | | Q | B Shelton | 2 | 1 | | | | |
| Q | A Kadhe | 5 | 5 | | | P Krstin | 6 | 0 | 1 | | | | | | | | |
| Q | B Shelton | 3 | 6 | 6 | Q | B Shelton | 4 | 6 | 6 | | | | | | | | |
| 7 | B Rola | 6 | 4 | 4 | | | | | | | | | | | Yo Watanuki | 6$^8$ | 4 |
| 4 | A Vukic | 6 | 6 | | | | | | | | | | | 4 | A Vukic | 7$^{10}$ | 6 |
| | T-l Wu | 3 | 3 | | 4 | A Vukic | 6 | 6 | | | | | | | | | |
| WC | A Kovacevic | 5 | 6 | 6$^5$ | Q | G Brouwer | 4 | 4 | | | | | | | | | |
| Q | G Brouwer | 7 | 3 | 7$^7$ | | | | | | 4 | A Vukic | 6 | 6 | | | | |
| | G Soeda | 6 | 6 | | | | | | | | G Soeda | 2 | 2 | | | | |
| | T-S Kwiatkowski | 1 | 4 | | | G Soeda | 6 | 5 | 6 | | | | | | | | |
| | M Torpegaard | 2 | 6 | 4 | 5 | J Jung | 4 | 7 | 4 | | | | | | | | |
| 5 | J Jung | 6 | 3 | 6 | | | | | | | | | | | | | |

### Bottom half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 6 | P Gunneswaran | 5 | 1 | | | | | | | | | | | | | | |
| WC | V Kirkov | 7 | 6 | | WC | V Kirkov | 6 | 6 | | | | | | | | | |
| | Em Nava | 3 | 6$^5$ | | | N Chappell | 2 | 3 | | | | | | | | | |
| | N Chappell | 6 | 7$^7$ | | | | | | | WC | V Kirkov | 3 | 2 | | | | |
| | K Uchida | 6 | 3 | | | | | | | 3 | J. J. Wolf | 6 | 6 | | | | |
| | Y Uchiyama | 4 | 1$^r$ | | | K Uchida | 3 | 4 | | | | | | | | | |
| | T Ito | 3 | 6 | 3 | 3 | J. J. Wolf | 6 | 6 | | | | | | | | | |
| 3 | J. J. Wolf | 6 | 3 | 6 | | | | | | | | | | 3 | J. J. Wolf | 2 | 3 |
| 8 | S Kozlov | 3 | 6 | 6 | | | | | | | | | | 8 | S Kozlov | 6 | 6 |
| | JC Aragone | 6 | 3 | 4 | 8 | S Kozlov | 6 | 6 | | | | | | | | | |
| Q | K Smith | 5 | | | Q | K Smith | 3 | 1 | | | | | | | | | |
| | M Mmoh | 3$^r$ | | | | | | | | 8 | S Kozlov | 6 | 6 | | | | |
| WC | Ezekiel Clark | 6 | 3 | 3 | | | | | | 2 | M Krueger | 4 | 4 | | | | |
| | C Harrison | 4 | 6 | 6 | | C Harrison | 3 | 6 | 4 | | | | | | | | |
| | N Mejía | 3 | 3 | | 2 | M Krueger | 6 | 1 | 6 | | | | | | | | |
| 2 | M Krueger | 6 | 6 | | | | | | | | | | | | | | |