Pogacar wins debut race of the season, keeping the momentum rolling after closing out 2019 on the podium of the Vuelta a Espana.
Young Slovenian attacked with five kilometers to go to put himself into overall lead with one stage remaining.
Haig slots into the overall lead, ahead of Pogačar, with Valverde in third.
The 21-year-old racing for UAE-Emirates, launched a last-minute attack to come around the favored Spaniard.
Spain's Volta a la Comunitat Valenciana will see Alejandro Valverde, Tom Dumoulin, Philippe Gilbert and other stars launch their respective 2020 racing campaigns.
Izagirre wins overall by seven seconds ahead of world champion Valverde. Dutch sprinter Groenewegen takes first victory of 2019.
Briton beats Valverde up steep final kick while Izagirre takes race lead with only one stage remaining.
The Olympic champion Van Avermaet follows Sanchez's canny move through a technical finale to win his first race of the season.
Italian Matteo Trentin scores his first victory of 2019 with a well-timed acceleration at the end of a hilly stage 2 in Spain.