Yorkshire are expecting a difficult start to their defence of the County Championship title away at newly-promoted Worcestershire at New Road on Sunday as the county season begins.
Five other matches start on Sunday, including Hampshire, who have also come up from Division Two, against Sussex.
Yorkshire coach Jason Gillespie knows his side are in for a tough first test.
"Worcestershire are a good side," Gillespie told BBC Radio Leeds. "We will need to bring our very best game."
He added: "They had four or five players who played every game last season and that is telling.
"They had good contributions throughout their line-up and we know not to underestimate anyone. They know their conditions well at home."
Elsewhere in Division One, Middlesex host Nottinghamshire and Durham face Somerset away at Taunton. In the second tier Northants face Gloucestershire and Leicestershire host Glamorgan.
Gillespie's Yorkshire side have signed India batsman Cheteshwar Pujara as their overseas player for the start of the season after Younus Khan pulled out of a proposed move to Headingley.
And with much of the side which ended their 13-year wait for a Championship title intact, including veteran bowlers Ryan Sidebottom and Tim Bresnan, Gillespie already knows who will be in his team come Sunday.
"I've been clear for a little while who'll be in our starting XI," he said.
"You always have an idea exactly what you want but these things can change."