CASTLE STUART, July 13, 2013 (AFP) - Mickelson joined tournament leader, Henrik Stenson in signing for a six under par 66 and end the round in a four-way share of second place on 14-under par and just two shots behind Stenson.
Stenson, 36, picked up seven birdies as he strives to win for the first time this year after being runner-up in April's Houston Open.
"I'm in a good spot at the moment and it would be the icing on the cake if I were to win tomorrow going into next week's Open," said Stenson.
The four-time major winning Mickelson, who is the highest ranked player in the field at number eight in the world, parred his opening seven holes before completing the last 11 in six under par, including grabbing three birdies in succession from the ninth hole on the Castle Stuart course.
Mickelson has 46 victories to his credit but just one victory in Europe and that was in 1993 in capturing a secondary Challenge Tour event near Euro Disney in France.
"Any victory over here would be terrific but then we are getting ahead of ourselves," said Mickelson.
"There's a packed leaderboard and it will take one good round of a shootout between 15 or 20 guys that are right there. I'm playing well and it feels terrific. I would love to win here in the UK especially on a links golf course."
Mickelson shares second place with South African Branden Grace (66), Denmark's JB Hansen (69) and England's John Parry (66). Northern Ireland's Gareth Maybin produced the lowest round of the day with an eight under par 64 to be tied in sixth place on 13-under par with Frenchman Raphael Jacquelin (65) and American Peter Uihlein (70).
While Stenson, Mickelson and Grace are already exempt into the British Open, Hansen, Parry, Maybin, Jacquelin and Uihlein will be seeking to secure victory that would see them also qualify.
Twenty-two players will go into the final round lying within six shots off the lead.
Leading scores from the third round of the Scottish Open at Castle Stuart on Saturday (par 72; GBR and IRL unless stated):
200 - Henrik Stenson (SWE) 70-64-66
202 - John Parry 64-72-66, JB Hansen (DEN) 68-65-69, Branden Grace (RSA) 71- 65-66, Phil Mickelson (USA) 66-70-66
203 - Gareth Maybin 69-70-64, Peter Uihlein (USA) 67-66-70, Raphael Jacquelin (FRA) 68-70-65
204 - Simon Khan 65-69-70, Matthew Southgate 69-64-71, Lorenzo Gagli (ITA) 67-67-70
205 - Chris Doak 66-66-73, Paul Casey 70-67-68, Tommy Fleetwood 70-67-68
206 - Ricardo Gonzalez (ARG) 70-68-68, Henni Otto (RSA) 70-70-66, Chris Paisley 70-65-71, Brooks Koepka (USA) 70-68-68, Martin Laird 68-69-69, Eddie Pepperell 69-69-68, Ross Fisher 68-65-73, Nicolas Colsaerts (BEL) 70-68-68