The 47-year-old sits at nine strokes under par for the tournament at TPC Sawgrass, one ahead of Matthew Fitzpatrick in second place. Sergio Garcia stood alone as the leader after a 65 in Round 1 but fell into a tie for third after he followed it up with a 72.
There is still a long list of competitors within striking distance with two days remaining, including big names like Bryson DeChambeau and Jon Rahm.
Round 2 Leaderboard
1. Lee Westwood (-9)
2. Matthew Fitzpatrick (-8)
T3. Sergio Garcia (-7)
T3. Chris Kirk (-7)
T5. Bryson DeChambeau (-6)
T5. Denny McCarthy (-6)
T5. Brian Harman (-6)
T5. Charley Hoffman (-6)
T5. Doug Ghim (-6)
T5. Sungjae Im (-6)
Full leaderboard and stats available at PGATour.com
Garcia was the star on Thursday and kept himself in contention with some more excellent shots throughout his second round.
The problem was his consistency—he carded five bogeys in Round 2 after having just one in his first round.
The 2008 Players Championship winner remains in contention but could have been in much better shape if he avoided mistakes.
It kept the door open for other players on the leaderboard and Westwood especially took advantage.
The English golfer thrived with a bogey-free round featuring some elite putting:
Westwood finished 4.365 strokes gained putting in the round to surge up the leaderboard despite not crushing it off the tee.
His attitude might have also helped him along the way:
Shane Bacon @shanebacon
I said it last week and it continues - nobody in the world looks like they're having more fun on a golf course than Lee Westwood is right now. So content, so happy, just out in a park walking around. Guessing just about every golf fan in the world is rooting for this to continue.
Fitzpatrick used a similar strategy to help him shoot 68 in Round 2. He reached 83.3 percent of greens in regulation and excelled with his putting on his way to six birdies:
Chris Kirk had the best round of the day with a 65 thanks to seven birdies and an eagle, putting him at seven-under for the tournament.
Even those a few strokes back can still climb in the next two rounds, including the red-hot DeChambeau after back-to-back rounds of 69. After his come-from-behind win at the Arnold Palmer Invitational last week, there is reason to believe in another comeback.
Jon Rahm, Justin Thomas and Patrick Reed are also under par for the week and shouldn't be counted out heading into the weekend.
Several big names are also heading home after missing the cut, including Xander Schauffele, Rory McIlroy, Tony Finau, Patrick Cantlay and Rickie Fowler.
These players will try to regroup before the Masters next month.